#

2+2

An innovative vehicle fuseholder that can hold two types of fuses - the MICRO and the JCASE, fuses which have differing circuit protection characteristics.

Back to top 

A

ABS

(Antilock Braking System) Computer, sensors and solenoid switches which together monitor wheel speed and modulate braking force if wheel lockup is sensed during braking. Helps the driver retain control of the vehicle during heavy braking on slippery roads.

ABYC

American Boat and Yacht Council, a voluntary body which sets standards for the marine industry.

ACTUATOR

The part of a switch assembly used by the operator that causes switch contacts to engage or disengage. Actuators include pushbuttons, levers, slides, keylocks, rockers and toggles. Cole Hersee switches offer you many ways of performing the same electrical function.

AFTERMARKET

Secondary market of the automotive industry, covering the installation of vehicle parts after the sale of the vehicle to the consumer. Aftermarket parts are parts that are installed on a vehicle once it has been sold to the enduser.

AFV

(Alternative Fueled Vehicle) Vehicle powered by a fuel other than gasoline or diesel.

AGA

A type of Glass Fuse also known as 1AG. These fuses are becoming uncommon - the last ones were installed in 1981 year cars,

AGC

A type of Glass Fuse also known as 3AG. These fuses are becoming uncommon - the last ones were installed in 1981 year cars,

AGC FUSE

A glass cylinder fuse, 1-1/4 inch long x 1/4 inch diameter with fast blow characteristics. Historically the AG stood for 'all glass' with a third lettter added to denote a particular type/size.

AGU

A type of Glass Fuse also known as 5AG. These fuses are becoming uncommon - the last ones were installed in 1981 year cars,

AGX

A type of Glass Fuse also known as 8AG. These fuses are becoming uncommon - the last ones were installed in 1981 year cars,

AIR RIDE SUSPENSION

Suspension which supports the load on air-filled rubber bags rather than steel springs. Compressed air is supplied by the same engine-driven air compressor and reservoir tanks which provide air to the air brake system.

ALTERNATING CURRENT

A flow of electrical current that increases to a maximum in one direction, decreases then reverses direction and reaches maximum in the other direction. This cycle is repeated continuously, many times per second. The number of such cycles per second is the frequency, measured in Hertz. US domestic current is 60 Hz (i.e. 60 cycles per second). Cole Hersee components are designed for DC, but many can be used with AC.

ALTERNATOR

Commonly refers to the DC charging device on an engine. The alternator is actually a three-phase AC device producing AC which is then rectified by a diode bridge to create direct current. In selecting a Battery Isolator, it's important to match the type of isolator to the alternator.

ALTERNATOR FIELD DISCONNECT

AFD. A safety feature of some master disconnect switches, such as Cole Hersee M-752 and M-753. If the output of an alternator is quickly open-circuited the voltage rises to a potentially dangerous level. An AFD disconnects the alternator field, so that the magnetic field is turned off, and thus the voltage does not spike.

AMMETER

Electrical test instrument used to measure current in a circuit.

AMPACITY

The current carrying capacity of a conductor or device.

AMPERE

AMPERE A The international unit of measurement for electrical current. Abbreviated to A, or amps. It is the rate of flow of electrons in a conductor. When electrons having a total charge of 1 coulomb pass a given point in one second, the current is equal to 1A.

It is named after the French physicist Andre Ampere (1775-1836). See Ohm's Law for calculations.

AMPERE-HOUR

The electric charge transferred past a specified circuit point by a current of one ampere in one hour. Ampere-Hour Rating (AH) A common rating for batteries. The total number of ampere-hours that a battery can deliver over 20 hours at a constant rate of discharge before the battery voltage falls below 10.5V.

APPARENT POWER

The product of voltage and current in a circuit.

APPLICATION

In Engineering, an application refers to a specific use for a device. For example, a Cole Hersee brand LVD finds an application in police cruisers (as well as many other uses).

ARC

Sparking that results when current flows through the air between two points of greatly differing potential. This can happen in overloaded switches. Cole Hersee switches are built to handle making and breaking of a circuit without significant arcing.

ARCING

Making an electrical arc or spark between two parts of a surface. It's an undesirable effect that can happen between the contacts of an electromechanical switch when the contacts are moved together or apart. Arcing can build up deposits on the contacts that cause inefficient conducting of current across the closed switch, and can create a build-up on the contacts which make tha matter worse. The situation can be ameliorated by using highly conductive contacts of copper or - better still - of silver, as in many Cole Hersee brand switches. Because there are no contacts or moving parts in electronic switches, there are no arcing problems.

ATO/ATC FUSE

The commonest fuse in the automobile industry. With a small plastic body and two blades. It has fast blow characteristics

AUTO-RANGING

A device is auto-ranging when it can 'sense' the supply voltage (such as 12V or 36V) and can operate according to that voltage. Such devices can be used at different voltages. Cole Hersee brand FlexMod LVDs 48610 is an example of an auto-ranging device. Many modern multimeters are auto-ranging. Autoranging devices are advantageous to the distributor - since an autoranging device may be usable at different voltage, a distributor need only stock one SKU, instead of several.

AUTOTRANSFORMER

A transformer used to step voltage up or down. The primary and secondary windings share common turns, and it provides no isolation.

AVI

(Automatic Vehicle Identification) System combining an on-board transponder with roadside receivers to automate identification of vehicles. Uses include electronic toll collection and stolen vehicle detection.

AWG

American Wire Gauge. This is the US standard for wire size.

AXLE

Structural component to which wheels, brakes and suspension are attached.

Drive axles are those with powered wheels.

Front axle is usually called the steer axle.

Pusher axles are unpowered and go ahead of drive axles.

Rear axles may be drive, tag or pusher types.

Tag axles are unpowered and go behind drive axles.

Back to top 

B

BATTERY

A collection of voltaic cells grouped together to provide higher voltage and/or higher current than a single cell. The battery is a common DC power source, especially for vehicles or equipment that is used remote from the domestic power supply.

Emergency vehicles and utility vehicles often have dual battery systems because of added power demand. Such systems necessitate the use of a Battery Selector Switch or a Low Voltage Disconnect Switch.

BATTERY BANK

When groups of batteries are wired in series or parallel or a combination to increase voltage or capacity the group is referred to as a battery bank. Batteries connected in series: the amps and amp-hour rating are the same and the voltage is additive. Batteries connected in parallel: the voltage is the same and the amps and amp-hour rating are additive. With two batteries (or banks of batteries) you’ll usually need some kind of control such as a battery selector switch, a battery isolator or a Smart Battery Isolator # 48525, 48530.

BATTERY DISCONNECT SWITCH

Master switch that disconnects a battery from the load. This provides a good measure of safety and security. Installation of such a switch is often mandatory to allow safe servicing operations. See 75920

BATTERY ISOLATOR

A solid state device that allows for the alternator to charge multiple batteries, and to control drain from one battery to the other. See 'Battery Isolators' and 'Smart Battery Isolator' #48530.

BATTERY MANAGEMENT

Commercial vehicles are increasingly adding electrical loads in order to provide more services. These range from computers, microvaves and air-conditioning in sleeper cabs on large trucks: to computers, GPS and flashbars on police vehicles: to tailgates on delivery trucks. To provide for added power demand, vehicles may need two batteries or banks of batteries. To efficiently manage the two batteries and prevent dead starting batteries, some kind of BATTERY MANAGEMENT may be needed, using Smart Isolators or Low Voltage Disconnect Switches.

BATTERY TYPE

AGM (Absorbed Glass Mat) Sealed lead-acid batteries that have the electrolyte absorbed in a bed of glass fibers, which holds the electrolyte next to the plate, and lessens the chance of spills. AGM batteries tend to have good power characteristics, low internal resistance, and good behavior during charging. Flooded cell battery Lead-acid batteries with an electrolyte of sulfuric acid. Flooded cells can generate gas while being charged. They must be periodically checked for fluid level and water added as necessary. They are also typically less expensive than AGM or gel cell type batteries. Gel cell Chemically the same as a flooded cell battery, but their electrolyte is in a gelatin form and is absorbed into the plates and the battery and sealed with epoxy resin. The batteries are leak resistant and may be used in any position.

BLIND SPOT

Areas around a commercial vehicle that are not visible to the driver either through the windshield, side windows or mirrors. Stickers on the rear of trucks remind other drivers "If you can't see me in my mirrors, I can't see you!" A unfortunate part of rig operation, which is being assisted by rear-view cameras.

BOBTAIL

Tractor operating without a trailer. Bobtailing is truckers' poetry for driving a tractor without a trailer.

BOLT

A threaded fastener with a head, designed to be used in conjunction with a nut. In contrast, a stud is a threaded fastener without a head, designed to be used with a nut.

BOLT-DOWN

Littelfuse's bolt-down type fuses protect circuits with medium to very high current loads. By using bolt connections, they are capable of protecting higher gauge cables. Bolt-down type fuses are available from Littelfuse in ampere ratings ranging from 30A to 500A. Types include MEGA and MIDI

BRAKE HORSEPOWER

BRAKE HORSEPOWER bhp
Engine horsepower rating as determined by brake dynamometer testing.

BREAK (Make and Break)

Make and break are terms which apply to any switching situation, but particularly to Intermittent Duty Solenoids, where the buildup of heat can cause failure of the component. Make and break are RATINGS. A particular component, such as a solenoid, may be rated for duty at a given amperage and voltage that should not be exceeded. Make is when the switch (or solenoid) is turned On (the circuit is 'made'), and break is when the switch is turned Off (the circuit is 'broken'). Such values would need to be checked with an instrument such as a meter. Note also that Intermittent Duty Solenoids have a limitation on the time (duty cycle) they may be kept On and the time they need to recover (to allow heat dissipation.)

BREAK BEFORE MAKE

When moving contacts interrupt one circuit before completing another. Also called non-shorting.

BREAKDOWN

The voltage at which an insulating material fails electrically.

BREAKER

A Circuit Breaker is similar to a fuse, but re-usable. It interrupts a current in an electric circuit when the current becomes too high. Unlike a fuse, a circuit breaker can be reset after it has been tripped. Circuit breakers are bimetallic thermal devices. Heating of the bimetalic strip caused by excessive current causes the strip to bend a break contact.

BTU

The British Thermal Unit is the power required to raise one pound of water through one degree Fahrenheit. One pound of water at 32 degrees F requires the transfer of 144 BTUs to freeze solid ice. The Watt (W) is the international standard of power.

BUSBAR

A rigid conductor used for electrical power distribution. In vehicles these busbars are usually made of brass or copper, or tin-plated copper. Cole Hersee sells simple busbars (see 56099-5 or 86126-4) or as part of Blocks (M-874, M-641-01, M-449).

Back to top 

C

CABOVER

(Cab-Over-Engine, COE) Truck or tractor design in which the cab sits over the engine on the chassis. Important in situations where overall length is important, especially in urban delivery situations. Often a less comfortable situation in a long haul, due to heat build up and lack of space within the cab. Driver's seat and passenger seat inevitably have to be accessed by separate doors in a COE.

CAPACITOR

Two plates or conductors separated by an insulator, used to store charge or to resist change in voltage.

CAPACITY

The current handling capability or rating of a switch. Alternatively refers to the amount of charge a component (like a capacitor) can hold - measured in Farads.

CARGO WEIGHT

Combined weight of all loads, gear and supplies on a vehicle.

CDL

(Commercial Driver's License) License which authorizes an individual to operate commercial motor vehicles and buses over 26,000 pounds gross vehicle weight. For operators of freight-hauling trucks, the maximum size which may be driven without a CDL is Class 6 (maximum 26,000 pounds gross vehicle weight).

CE

CE (Conformité Européenne) The CE marking is a logo which denotes conformity to European standards. It consists of the stylized letters “CE”. The CE marking is put on products regulated by European health, safety and environmental protection legislation, and is obligatory for certain products sold in Europe.

CELL

An electrochemical system that converts chemical energy into electrical energy. It typically consists of two conductive plates with different galvanic potential, immersed in an electrolyte. A battery is several cells connected together.

CEN

The European Committee for Standardization.

CFR

(Code of Federal Regulations) The written regulations of the United States Federal Government.

CHARGE

The accumulation of electrons producing an electrostatic charge. In common use it often refers to energy content of a battery.

CHASSIS WEIGHT

(Curb Weight, Tare Weight) Weight of the empty truck, without occupants or load.

CIRCUIT

A closed path (or loop) of electrically (or electromagnetically) connected components or devices that is capable of current flow. Typically consists of loads, sources, conductors, and circuit protection (circuit breakers and fuses). The path must be continuous and closed.

COAST TO PARK

Non-dynamic (coast to park) and dynamic braking or parking refer to Windshield Wiper Switches. Your vehicle has either one of the systems for bringing the wipers to the home or parked position. If you are replacing a switch, you need to know which type it is. Consult your Vehicle Owner's Manual. For those who need to know how they work, read on... Dynamic brake: Essentially, when you turn the wipers Off, they stop when they reach their park position, but they also get retarded electrically to bring the motor to a rapid stop. When you turn the wiper switch Off and the wipers reach the park position (left or right), the armature of the wiper motor is disconnected from the load and immediately connected across ground. The motor then functions as a loaded generator and develops a retarding torque that rapidly stops the motor. Non-dynamic brake: Essentially, when you turn the wipers off, they stop when they reach their park position. When you turn the wiper switch Off the wipers continue to run by a separate set of contacts mounted on the motor, until the wipers reach their park position. At this point the contacts open, removing power, and thereby stopping the wiper motor. If the motor is not in the park position for the wipers, it continues to run until it reaches the park position and the switch opens as before.

COEFFICIENT OF FRICTION

A dimensionless number representing the ratio of the friction force to normal force. Typically for threaded connections it is between 0.10 to 0.18 but can vary significantly depending upon the materials used and whether a lubricant has been employed.

COMMON CARRIER

Freight transportation company which serves the general public. May be regular route service (over designated highways on a regular basis) or irregular route (between various points on an unscheduled basis).

CONTACT GAP

The open distance between contacts.

CONTACTS

A pair of devices that touch or come apart at the point where the switch throw makes or breaks the circuit. Silver contacts are common because of their low conductivity and low electrical resistance. Many Cole Hersee switches have silver contacts.

CONTAINER

(Shipping Container) Standard-sized rectangular box used to transport freight by ship, rail and highway. International shipping containers are 20 or 40 feet long, conform to International Standards Organization (ISO) standards and are designed to fit in ships' holds. Containers are transported on public roads atop a container chassis towed by a tractor. Domestic containers, up to 53 feet long and of lighter construction, are designed for rail and highway use only.

CONTINUOUS

Certain switches, like solenoids can be rated for continuous or intermittent (infrequent) use. A comparably-constructed switch can generally be used with a higher current than the other switch, but with the proviso that a cooling time is allowed. There are no such restrictions on a 'continuous duty' switch. You can use a Continuous Duty Solenoid instead in place of an Intermittent Duty Solenoid, but it would have a shorter life expectancy compared to the purpose-built Intermittent Duty Solenoid. You cannot use an Intermittent Duty Solenoid in place of a Continuous Duty Solenoid!

CONTRACT CARRIER

Company that transports freight under contract with one or a limited number of shippers.

CONVERTER

A device which changes alternating current (AC) to direct current (DC)

CORE

The iron (or ferrous material) center part of a transformer used to increase the strength of the magnetic field, or the moving part in a solenoid switch.

COULOMB

The unit of electrical charge equivalent to the total negative electrical charge of 6.24 x 10(18) electrons. One coulomb per second equals a current flow of 1A.

COULOMB

The measurement unit of flow of electric charge. The SI unit of electrical charge equal to the quantity of charge transferred in one second by a steady current of one ampere.

CRANKING

The current drawn by the starter circuit prior to engine starting. Actual current varies considerably during the starting cycle. A large surge of current is required at first to overcome the inertia and compression of the engine, then it settles down to a level with less violent fluctuations as the pistons go through compression and exhaust cycles. The cranking current rating is used as a guide for selection of batteries, cables and battery switches.

CSA

Canadian Standards Association, a Canadian rating organization. Sorry, US Civil War fans. It does not here refer to the Confederate States of America... not unless they got north of the border!

CUBE

(Cubic Capacity) Interior volume of a truck body, semitrailer or trailer, measured in cubic feet.

CURRENT

The movement of electrons through a conductor. Measured in amperes (A).

CURRENT RATING

This is the maximum current in amperes that a switch will carry (at a steady state under defined conditions) without exceeding specified performance limits.

CUSTOM

We do custom switches! Sometimes it's just a question of text on a knob, or a custom bezel, or a special key with the manufacturer's name on it. Other times we can take a standard switch and add a seal, or change the terminals. Other times a customer wants a ground-up solution to a switching problem. We can do that!

Back to top 

D

DEAD BATTERY

The bane of a motorist's day! But a dead battery for a working vehicle could add up to a minimum $1000 road call. Add to that the downtime of the driver, and a dead battery is a costly situation. If the driver tries to continue cranking, he could destroy or severely reduce the performance of his battery. Cole Hersee has many solutions to such a problem, such as the installation of a Low Voltage Disconnect Switch.

DEAD-HEADING

Operating a truck without cargo, either on the outbound or inbound leg. A situation to be avoided!

For you gardeners, it's signifies removal of faded blooms in order to encourage setting of flowers.

DECIBEL

The standard unit for expressing relative power levels. Decibels indicate the ratio of power output to power input. 1 dB = 10 log10.

DEEP CYCLE

Deep-cycle batteries have thick plates reserve energy to be stored within the battery plate and released during slow discharge for prolonged periods.Such a battery is relatively ineffective for ignition, but will supply a steady amount of power for a long time better than a cranking battery will.

DELAY

A difference in time between the start of an event and its occurrence. Typically used in descriptions of fuses. A fuse with a short delay trips faster, but in many cases, a longer delay may be desirable.

DELCOTRON

A tradename of AC-Delco. In this context, 'Delcotron-type' refers to 4-stud Battery Isoiators such as the cole Hersee 48092. Other Battery Isolators, such as 48070 have three studs. You can use a 4-stud Battery Isolator in a 3-stud application (by not connecting the 4th stud) but not vice-versa.

DEPENDENT

Illuminated Rocker or Toggle Switches have dependent or independent illumination. The pilot light on the DEPENDENT switch is On when the switch is actuated and the load is energized (and Off when it's not). The pilot light on an INDEPENDENT switch is turned On by an external switch, whether load is On or Off. It may at first seem counterintuitive, but the pilot lights of an INDEPENDENT switch are independent of the state of the switch.

DERATING

A decrease in a the rating of a switch to accommodate different conditions in which it is to be used. When a switch is to be used at a higher voltage at which a specification is cited, the amperage needs to be derated. For example, a switch rated for 20A at 12V can be used with a safe current of 10A when used at 24V. This is a typical application of Ohm's Law. Warning: not all switches should be derated in this way. This is true of lighted switches where the lighting circuit must function only at rated voltage

DETENT

A feature on some switches that indicates that the actuation point has been reached. Also referred to as tactile feel. Some detents emit an audible click to provide feedback to the user.

DIELECTRIC STRENGTH

The capability of of nonconducting material to withstand a maximum voltage.

DIESEL

Diesel engines, unlike gasoline engines, do not need a spark plug. They rely instead on a compression cycle , which is self-sustaining. However, a cold engine block easily dissipates heat, and a glow plug is necessary to start the cycle. Thus ignition switch for diesel engines differ from those used for gasoline engines. See 956-5100 and 95033.

DIGITAL DATABUS

An electronic circuit that carries digital data, or ‘information’.

DIMMER

We manufacture Headlamp dimmer switches such as 7786, which is floor-operated; rotary dimmer switches for internal lights such as 74601-01 and Push-Pull switches that also have a rotary dimming feature, such as 71092-02.

DIRECT CURRENT

(DC) Electrical current which flows in one direction only. All battery-driven circuits are DC.

Cole Hersee manufactures switches and components for DC applications.

DISPLACEMENT

(Piston Displacement) Sum of the volumes swept by an engine's pistons as they travel up and down in their cylinders. Based upon bore (diameter of cylinder) and stroke (distance traveled by piston). Expressed in liters or cubic inches.

DMM

(DIGITAL MULTIMETER) An instrument used to measure voltage, current and resistance. It is rapidly replacing the traditional galvanometer multimeter, which is fragile.

DOUBLE BREAK

A mechanism which breaks the circuit at two points simultaneously. You can use a Double Pole Master Disconnect Switch to create a double break, for added electrical security. One part of the switch breaks the positive line; the other breaks the negative. See # 75912.

DOUBLE THROW (DT)

Contact arrangement that alternately transfers normally open and normally closed circuits.

DPDT

Double Pole, Double Throw. Circuitry which describes a switch. Double Pole means that this switch controls two circuits. It's like having two switches in one switch body, except that the switching action is the same in both. Double Throw means that this switch has two On positions. It could be an On-On or an On-Off-On. It's likely to be an On-Off switch - but it controls two independent circuits.

DPST

Double Pole, Single Throw. Circuitry which describes a switch. Double Pole means that this switch controls two circuits. It's like having two switches in one switch body, except that the switching action is the same in both. Single Throw means that this switch has one On position. It's likely to be an On-Off switch - but it controls two independent circuits.

DRIVELINE

All the components which together transmit power from the transmission to the drive axle(s). These consist of at least one driveshaft (propeller shaft) with a universal joint at each end.

DRIVETRAIN

(Powertrain) All the components, excluding engine, which transmit the engine's power to the rear wheels: clutch, transmission, driveline and drive axle(s).

DRL

(Daytime Running Lights) System that automatically turns on a vehicle's low beam headlights when the parking brake is released and the ignition is on. Cole Hersee part number 48600 (D-559).

DUAL BATTERY SYSTEM

Two batteries mounted on a vehicle. Large vehicles often have dual battery systems because of added power demand. Such systems necessitate the use of Battery Selector Switches, Battery Isolators or Low Voltage Disconnect Switches (LVDs) 

DYNAMIC BRAKE

Non-dynamic (coast to park) and dynamic braking or parking refer to Windshield Wiper Switches. Your vehicle has either one of the systems for bringing the wipers to the home or parked position. If you are replacing a switch, you need to know which type it is. Consult your Vehicle Owner's Manual. For those who need to know how they work, read on... Dynamic brake: Essentially, when you turn the wipers Off, they stop when they reach their park position, but they also get retarded electrically to bring the motor to a rapid stop. When you turn the wiper switch Off and the wipers reach the park position (left or right), the armature of the wiper motor is disconnected from the load and immediately connected across ground. The motor then functions as a loaded generator and develops a retarding torque that rapidly stops the motor. Non-dynamic brake: Essentially, when you turn the wipers off, they stop when they reach their park position. When you turn the wiper switch Off the wipers continue to run by a separate set of contacts mounted on the motor, until the wipers reach their park position. At this point the contacts open, removing power, and thereby stopping the wiper motor. If the motor is not in the park position for the wipers, it continues to run until it reaches the park position and the switch opens as before.

Back to top 

E

EDI

(Electronic Data Interchange) The business-to-business interconnection of computers for the rapid exchange of a wide variety of documents, from bills of lading to build tickets at auto plants.

ELECTROMECHANICAL DEVICE

A mechanical device which is controlled by an electric device. Solenoids and circuit breakers are examples.

EMF

Electromotive force or voltage (V).

Back to top 

F

FARAD

FARAD F The farad is the SI unit of the capacitance of an electrical system, that is, its capacity to store electricity. It is a rather large unit as defined and is more often used as a microfarad.

It is named after the English chemist and physicist Michael Faraday (1791-1867).

FAST ACTING

Refers to the amount of time that a fuse (or circuit breaker) can endure an over-current before blowing (or tripping). Fast fuses are used to protect sensitive equipment. Littelfuse is a pioneerin the development of fast-acting fuses. Recent introductions include the MICRO2 and MICRO3 fuses. And, of course, we learn from TV that it also refers to Alka-Seltzer!

FAULT

A defect in the normal circuit configuration, usually due to unintentional grounding. Commonly referred to as a short circuit.

FERROUS

Made of iron or an alloy of iron (such as steel). Most iron alloys have the property of being magnetic. Because of this, plungers in an electromechanical solenoid are made of a ferrous material.

FIELD

Typically refers to a magnetic field. Specifically used when discussing the rotating electromagnetic field associated with an alternator. By varying the field current, thus its strength, the output of the alternator may be controlled.

FIFTH WHEEL

Coupling device attached to a tractor or dolly that supports the front of a semitrailer and locks it to the tractor or dolly. The fifth wheel's center is designed to accept a trailer's kingpin, around which the trailer and tractor or dolly pivot in turns.

FIT

Class of Fit is a measure of the degree of fit between mating internal and external screw threads. Three main Classes of Fit are defined for metric screw threads : FINE: A tolerance class of 5H for internal threads and 4h for external threads. MEDIUM: A tolerance class of 6H for internal threads and 6g for external threads. COARSE: A tolerance class of 7H for internal threads and 8g for external threads. For Unified threads, a similar designation as for metric threads is used. The thread classes used are 1A, 2A and 3A for external threads and 1B, 2B and 3B for internal threads.

FLEC

Littelfuse Flexible Electrical Center - a sealed container that accepts a high density of circuit protection devices of all kinds, and is configurable to user schematics.

FlexMod

A Cole Hersee proprietary name for a small (4x3x1") versatile control unit. Available as a Low Voltage Disconnect #48610, a Timer #48636, a Smart Battery Isolator Controller #48540, and as a Voltage and Time unit #48541.

FORM FACTOR

As used here - the physical size of a component. The term may be used differently in different disciplines.

FORWARD & REVERSE

A common need in a switch, which needs to be DPDT Mom On - Off - Mom On. Forward/reverse switching can be used in other operations: up/down, wind up/wind out, front/back, in/out etc, covering many applications from snowplows to tailgate operation. Switching can be achieved by module 24451, rotary switch such as 90005-01, a rocker switch such as 58027-18 or a toggle such as 55046.

FRICTION

Mechanical resistance to the relative movement of two surfaces. There are two main types of friction; STATIC FRICTION (when two bodies are standing still, relative to each other)and DYNAMIC FRICTION. Typically static friction is greater than dynamic friction.

FUSE

A safety device, consisting of a strip of low-melting-point alloy, which is inserted in an electric circuit to prevent excess current from flowing. If the current becomes too high the alloy strip melts, opening the circuit, and protecting the components in the circuit. A fuse is the deliberate weak link in a circuit. And you've come to the right place for fuses! Littelfuse is the world's largest manufacturer of fuses.

FUSE HOLDER

There are many types of DC fuses... and there are many types of fuse holder. Holders are designed as a receptacle for a single fuse of any type, or several fuses of the same type, or they even accept different types of fuses such as the Littelfuse brand 2+2 which takers MINI and JCASE fuses. Other fuseholder receptacles such as the HWB18 and HWB60 not only accept fuses, but circuit breakers and diodes. The Littelfuse FLEC receptacle is large enough to hold a wide series of circuit protection devices. Fuseholders protect the devices they contain against damage, loosening from their socket, or against infiltration of water and dirt,

Back to top 

G

GALVANIC SERIES

A list of metals and alloys arranged in order of their potentials when immersed in seawater. The table of potentials is arranged with the anodic or least noble metals at one end, and the cathodic or most noble metals at the other. When making metallic connections, it is important to juxtapose appropriate metals in the series, to avoid galvanic corrosion, especially in marine environments.

GEAR RATIO

Number, usually expressed as a decimal fraction, representing how many turns of the input shaft cause exactly one revolution of the output shaft. Applies to transmissions, power takeoffs, power dividers and rear axles. Example: If 2.5 revolutions of an input shaft cause one revolution of the output shaft, the gear ratio is 2.5:1.

 

GVW (Gross Vehicle Weight)

Total weight of a vehicle and everything aboard, including its load.

GVWR (Gross Vehicle Weight Rating)

Total weight a vehicle is rated to carry by the manufacturer, including its own weight and the weight of its load.

GENERATOR

A machine with rotating parts that is capable of generating electrical power. In the narrow definition 'generator' refers to a DC machine and 'alternator' refers to an AC machine. Sometimes the term generator is used to refer to AC machines as well.

GLOWPLUG

Diesel engines, unlike gasoline engines, do not need a spark plug. They rely instead on a compression cycle , which is self-sustaining. However, a cold engine block easily dissipates heat, and a glow plug is necessary to start the cycle. Thus ignition switch for diesel engines differ from those used for gasoline engines. See 956-5100 and 95033.

Back to top 

H

HAZMAT

Hazardous materials, as classified by the US Environmental Protection Agency (EPA). Transport of hazardous materials is strictly regulated by the U.S. Department of Transportation.

HDAW

Heavy Duty Aftermarket Week. An important meeting and tradeshow in the heavy automotive trade.

HERTZ

Hz The hertz is the SI unit of the frequency of a periodic phenomenon. One hertz indicates that 1 cycle of the phenomenon occurs every second. For most work much higher frequencies are needed such as the kilohertz [kHz] and megahertz [MHz].

It is named after the German physicist Heinrich Rudolph Hertz (1857-94).

HIGH INRUSH

Loads that require more current when first turned on than is needed to continue operation. Light bulbs exhibit high resistive inrush and may draw up to 10 times or more the normal operating current when first turned on. Motors may show high inductive inrush currents when started. Switches and other components often need to be capable of handling such conditions.

HORSEPOWER

(hp) Measure of power (the amount of work that can be done over a given amount of time). One horsepower is defined as 33,000 foot-pounds of work in one minute. Example: Lifting 33,000 pounds one foot in one minute, or lifting 3300 pounds ten feet in one minute.

HWB

A Littelfuse 'hard-wired box' or sealed holder of plug-in circuit protection devices. Available as HWB18 - with 18 blade slots, or HWB60 with 60 blade slots.

Back to top 

I

IBEX

International Boatbuilders' Exhibition and Conference. The leading marine industry annual meetiing and tradeshow in North America. Cole Hersee has mainted a booth at this show ever since it was founded.

IDLE REDUCTION

Idling refers to an engine that's running but not powering the gear train (moving the vehicle). There are may reasons that vehicles are idled. They could be stopped while a driver makes a quick delivery, or they could be run overnight to keep and appropriate temperature within a cab or passenger vehicle. Clearly such a stationary vehicle creates undesirable emissions, and adds to pollution... and now can attract substantial fines!

IDLING

Allowing the engine to run when the vehicle is stationary. This is done for several reasons, most often to maintain comfortable cab temperature in hot or cold situations.

States and cities are increasingly imposing anti-idling regulations (with substantial fines!) which limit the time an engine may be run at idle. Use of a heater or air-conditioning without idling can impose a significant drain on the battery... a situation that can be corrected by installing a LVD (Low Voltage Disconnect Switch).

IGNITION-PROTECTED

Electromechanical switches inevitably tend to create a spark between the contacts. In normal circumstances this is unlikely to be a problem, but in confined situations where fuel vapors may be present (In boats and in mines for example), ignition-protected switches are necessary. ISO 8846 is a marine standard of the International Organization for Standards. Many Cole Hersee brand ignition switches are cerified to this standard.

INDEPENDENT

Illuminated Rocker or Toggle Switches have dependent or independent illumination. The pilot light on the DEPENDENT switch is On when the switch is actuated and the load is energized (and Off when it's not). The pilot light on an INDEPENDENT switch is turned On by an external switch, whether load is On or Off. It may at first seem counterintuitive, but the pilot lights of an INDEPENDENT switch are independent of the state of the switch.

INDUCTANCE

An effect in electrical systems in which electrical currents store energy temporarily in magnetic fields before that energy is returned to the circuit.

INDUCTOR

A length of wire that is wound around a core that is used as a storage element for a magnetic field in an electric circuit.

INRUSH

Inrush is the maximum instantaneous input current drawn by an electrical device when first turned on. For example, incandescent light bulbs have high inrush currents until their filaments warm up and their resistance increases. Devices are designed to cope with inrush current, and knowledgeable electricians will make sure a circuit can safely handle such a surge, and match it with appropriate circuit protection.

INRUSH CURRENT

The initial surge current demand before the load resistance or impedance increases to its normal operating value.

INTERMITTENT

Some switches are designed for infrequent (or intermittent) use. Devices such as solenoids may need a cooling period before they should be re-actuated. Rating a switch for intermittent use typically allows it to operate at a higher current than might otherwise be recommended. See CONTINUOUS. You can use a Continuous Duty Solenoid in place of an Intermittent Duty Solenoid, but it would have a shorter life expectancy compared to the purpose-built Intermittent Duty Solenoid. DO NOT use an Intermittent Duty Solenoid in place of a Continuous Duty Solenoid!

INVERTER

A device used to change DC into AC power.

IP67

IP numbers refer to INGRESS PROTECTION of a device against ingfress of dust or liquid. A switch with a rating of IP67 will resist spraying with a high pressure hose. A switch with IP68 is even more resistant. These are the two most useful numbers when you're considering spec'ing a switch.

IP68

IP numbers refer to INGRESS PROTECTION of a device against ingfress of dust or liquid. A switch with a rating of IP67 will resist spraying with a high pressure hose. A switch with IP68 is even more resistant. These are the two most useful numbers when you're considering spec'ing a switch.

ISO 8846

Electromechanical switches inevitably tend to create a spark between the contacts. In normal circumstances this is unlikely to be a problem, but in confined situations where fuel vapors may be present (In boats and in mines for example), ignition-protected switches are necessary. ISO 8846 is a marine standard of the International Organization for Standards. Many Cole Hersee brand ignition switches are cerified to this standard.

ISOLATION TRANSFORMER

A multiple winding transformer with primary and secondary windings physically separated and designed to permit magnetic coupling between isolated circuits.

Back to top 

J

JIT

(Just-In-Time) Manufacturing system which depends on frequent, small deliveries of parts and supplies to keep on-site inventory to a minimum. Cole Hersee Co. uses this and other systems to improve efficiency and maximize throughput.

JOULE

JOULE J The joule is the unit of work or energy. One joule is the amount of work done when an applied force of 1 newton moves through a distance of 1 meter in the direction of the force.

A watt second. 1 joule equals 0.0002778 watt hours. 1 kilowatt hour is equivalent to 3,600,000 joules.

It is named after the English physicist James Prescott Joule (1818-89).

Back to top 

K

KELVIN

KELVIN K The kelvin is the basic unit of temperature. It is 1/273.16th of the thermodynamic temperature of the triple point of water.

It is named after the Scottish mathematician and physicist William Thomson 1st Lord Kelvin (1824-1907).

KEPS NUT

A pre-assembled nut and washer assembly a trademark of ITW Shakeproof. The origin of the word came from shaKEProof.

KEY SWITCH

Switches come with many kinds of actuator such as a rocker or toggle. In a rotary switch , you need to rotate a knob. When the function you're controlling needs to be locked (like an ignition), then a KEY SWITCH is a useful item. But it's not just ignitions that need to be locked down. Vehicles may need to be immobilized using a Master Disconnect Switch such as 75920, and keyed rorary switches like 95060 can be used for many general purposes as well as for ignition.

KEYWAY

In toggle switches, a groove cut across the threads of the mounting stem. Toggle switches are generally mounted ithrough a circular hole in the panel, and secured by tightening a nut against the panel. Sometimes the nut can loosen ciusing rotation of the switch. Some panels are pre-cut with holes that have a small projection which engages with the keyway, thus preventing potentiol switch rotation.

KILO

A prefix in the metric system equal to 1000 times, as in kiloHertz, 1000 cycles per second, or as in kilogram, and many other combinations.

KILOGRAM

KILOGRAM kg The kilogram is the basic unit of mass. It is the mass of an international prototype in the form of a platinum-iridium cylinder kept at Sevres in France. It is now the only basic unit still defined in terms of a material object, and also the only one with a prefix [kilo] already in place.

kW

1000 watts

KWH

Kilowatt hours (kW times hours) A measurement of power and time used by utilities for billing purposes.

Back to top 

L

LATCHING

Provide a control current to a solenoid and it will maintain the power circuit as long as you maintain the control current. Stop the control current and the power current stops. Because of their many windings, there's a concomitant heat build-up in a solenoid that is not desirable. With a LATCHING SOLENOID, you provide a control current and the plunger clicks into position and maintains the power current, even when you remove the control current. Supply control current again and the plunger latches Off and switches the power current Off. Check out our Latching Solenoid 24200 and our Dual Relay 48521.

LED

Light-emitting diode. LEDs are electronic lights. As such they draw far less current that conventional incandescent lights, and they are far more efficient. Check out our PL-612 series pilot lights and 58312 series LED rocker switches. Although there's a trend to replacing incandescent lighting with LED, there are plenty of users with incandescent lighting - and we will continue to stock incandescent. If you change from incandescent to LED, remember you will need to replace your fuses with lower amperage types.

LIGHT TRUCK

A vehicle with an average weight of less than 10,000 pounds (according to the US Census Bureau’s 2002 Vehicle Inventory and Use Survey). Over this weight but under 19,500 is a Medium Truck.

LISTED

'UL Listed' Indicates that a device or component has met certain specifications as established by Underwriters Laboratory. It means that the device or component has been tested for conformance and is with UL so the device can be maked with the UL logo and the manufacturer claims conformance to the appropriate specification. Note that the ratings on UL electrical devices can be very conservative!

LOAD

The device that uses the power supplied from an electrical source. It can be a motor, lamp, horn or other device.

LOCK NUT

A nut which provides extra resistance to vibration loosening, by providing some form of prevailing torque.

LOCK-OUT

A safety precaution in which a switch is secured with a padlock to prevent accidental actuation. Such actions may be required by regulations such as those mandated in the US by OSHA. See 75920 Master Disconnect Switch, which can be readily locked-out or tagged-out.

LTL

(Less-Than-Truckload) A quantity of freight less than that required for the application of a truckload (TL) rate; usually less than 10,000 pounds.

LVD

Low Voltage Disconnect Switch.
A versatile electronic unit that conserves vehicle starting power by shedding auxiliary loads and reconnecting them when battery is replenished.
Some LVDs can be programmed to an array of parameters such as time or voltage levels.

Available in different sizes/amperages:

48512 (150A) and 48510 are 6 x 5.25 x 3"

48513 (100A at 12V or 24V DC) is 4.5 x 4.25 x 3"

48510 (10A at 12V or 24V DC) is only 4 x 3 x 1"

 

Back to top 

M

MAGNETO

A magneto is a generator of electrical current that uses permanent magnets. Magnetos are typically used on gasoline engines that do not have batteries associated with them, such as lawnmowers and chainsaws. The pulling of a lanyard drives a magneto that creates the initial ignition spark. See Magneto switch 95539

MAINTAINED CONTACT

For switching purposes, MAINTAINED CONTACT is the opposite of MOMENTARY CONTACT. A momentary switch is spring-loaded - press the actuator and it moves; remove your finger and it returns to its original position. With a maintained contact switch, you move the actuator, and it stays put until you move it again. Some simple switches are TOGGLED - you press to On, press again to Off.

MAKE (Make and Break)

Make and break are terms which apply to any switching situation, but particularly to Intermittent Duty Solenoids, where the buildup of heat can cause failure of the component. Make and break are RATINGS. A particular component, such as a solenoid, may be rated for duty at a given amperage and voltage that should not be exceeded. Make is when the switch (or solenoid) is turned On (the circuit is 'made'), and break is when the switch is turned Off (the circuit is 'broken'). Such values would need to be checked with an instrument such as a meter. Note also that Intermittent Duty Solenoids have a limitation on the time (duty cycle) they may be kept On and the time they need to recover (to allow heat dissipation.)

MASTER DISCONNECT SWITCH

Master switch that disconnects a battery from the load. This provides a good measure of safety and security. Installation of such a switch is often mandatory to allow safe servicing operations of vehicles.

Check out switch 75920

MEDIUM TRUCK

A vehicle with an average weight of less than 19,500 pounds and over 10,000 pounds (according to the US Census Bureau’s 2002 Vehicle Inventory and Use Survey). 10,000 or under is a Light Truck.

MEGA

MEGA M A metric prefix meaning a magnitude of 1,000,000 or 10^6.

METER

METER or METRE m The meter is the basic unit of length. It is the distance light travels in a vacuum in 1/299792458th of a second.

METRIC PREFIXES

The Systeme International (SI) is the worldwide metric system. It allows the sizes of units to be made bigger or smaller by the use of appropriate prefixes.

For example, the electrical unit of a watt is not a big unit even in terms of ordinary household use, so it is generally used in terms of 1000 watts at a time. The prefix for 1000 is kilo so we use kilowatts [kW] as our unit of measurement. For makers of electricity, or bigger users such as industry, it is common to use megawatts [MW] or even gigawatts [GW].

yotta Y 1 000 000 000 000 000 000 000 000 10^24

zetta Z 1 000 000 000 000 000 000 000 10^21

exa E 1 000 000 000 000 000 000 10^18

peta P 1 000 000 000 000 000 10^15

tera T 1 000 000 000 000 10^12

giga G 1 000 000 000 a billion

mega M 1 000 000 a million

kilo k 1 000 a thousand

hecto h 100

deca da 10

1

deci d 0.1

centi c 0.01

milli m 0.001 a thousandth

micro µ 0.000 001 a millionth

nano n 0.000 000 001 a thousand millionth

pico p 0.000 000 000 001 10^-12

femto f 0.000 000 000 000 001 10^-15

atto a 0.000 000 000 000 000 001 10^-18

zepto z 0.000 000 000 000 000 000 001 10^-21

yocto y 0.000 000 000 000 000 000 000 001 10^-24

[µ] the symbol used for micro is the Greek letter mu.
Nearly all of the S I prefixes are multiples or sub-multiples of 1000. However, these are inconvenient for many purposes and so hecto, deca, deci, and centi are also used. Deca also appears as deka [da] or [dk] in the USA and Continental Europe.

MICRO

MICRO µ A metric prefix meaning one millionth of a unit or 10^-6.

MICRO3

A type of vehicle fuse introduced by Littelfuse - one of the smallest you can obtain. The value of small fuses is that the vehicle manufacturer can squeeze many fuses into a small space - an important consideration as more circiuts are being designed-in to vehicles to provide additional functions. The clever part about the MICRO3 is that it has three blade terminals compared to other similar fuses... and that it contains two fused circuits. A vehicle OEM can therefore get twice as many fuses into the same space!

MICRON

A metric term meaning one millionth of a meter.

MIL

A unit of length equal to one-thousandth, 10^-3 of an inch.

MILLI

MILLI m A metric prefix meaning one thousandth of a unit or 10^-3.

MINI

A type of blade fuse patented by Littelfuse, characterized by its small size, so that many can be packed into a small fusebox.

MOLYBDENUM DISULPHIDE

A solid lubricant for bolts that acts as a high pressure resistant film. Can be used by itself as a dry lubricant as well as in with other solid lubricants and in oils and greases. Such lubricants act as a separating film to prevent corrosion formation on the thread surface (even under adverse temperature and environmental conditions) ensuring the release of the threaded connection.

MOMENTARY

We sometimes call it a "Mom". A momentary switch is spring-loaded - press the actuator and it moves; remove your finger and it returns to its original position. The oppsite type is a maintained contact switch. You move the actuator, and it stays put until you move it again. We have 'Moms' in all kinds - Push-pull, pushbutton, rotary, toggle and rocker, for example. Some simple switches are TOGGLED - you press to On, press again to Off.

MTBF

(Mean Time Between Failure) the probable length of time that a component taken from a particular batch will survive if operated under the same conditions as a sample from the same batch. An important engineering concept that is employed at Cole Hersee to ensure reliablity.

Back to top 

N

NANO

NANO (N) A metric prefix meaning one billionth of a unit or 10-9.

NEC

The NEC is developed and maintained by the National Fire Protection Association which describes how residential, commercial, and RV electrical systems must be installed. The NEC is adopted by states that also adopt the Uniform Building Code. Electrical inspections required by most building permits follow the NEC.

NEMA

The National Electrical Manufacturers Association.

NEWTON

NEWTON N The newton is the SI unit of force. One newton is the force required to give a mass of 1 kilogram an acceleration of 1 meter per second per second.

It is named after the English mathematician and physicist Sir Isaac Newton (1642-1727).

It's also the name given to a well-known cookie devised by the United Biscuit Co., and named after a town near Boston. What American has not enjoyed a Fig Newton?

NMEA

The National Marine Electronics Association of the USA.

NON-ARCING

Arcing is creating an electrical arc or spark between two parts of a surface. It's an undesirable effect that can happen between the contacts of an electromechanical switch when the contacts are moved together or apart. Arcing can build up deposits on the contacts that cause inefficient conducting of current across the closed switch, and can create a build-up on the contacts which make tha matter worse. The situation can be ameliorated by using highly conductive contacts of copper or - better still - of silver, as in many Cole Hersee brand switches. Electronic switches are NON-ARCING because they contain no contacts or moving parts.

NTEA

The National Truck Equipment Association, which organizes the annual Work Truck Show.

Back to top 

O

OCTAGON HEAD

A bolt or screw whose head cross-section is a regular polygon with 8 sides. Most screw and bolt heads are hexagonal.

OEM

Original Equipment Manufacturer. In the automotive industry, this term refers to automotive and heavy vehicle manufacturers. However, generally it can also refer to the manufacturer of any finished product.

OHM

The unit of measurement for electrical resistance or opposition to current flow. Its symbol is the uppercase Greek letter omega.

It is named after the German physicist Georg Simon Ohm (1789-1854).

OHM'S LAW

The all-important relationship between voltage (pressure), current (electron flow), and resistance. The current in an electrical circuit is directly proportional to the voltage and inversely proportional to the resistance. E=IR, or I=E/R, or R=E/I. Where E=voltage, I=current, and R=resistance.

OPERATING POSITION

Position of the actuator at which the contacts operate.

OSHA

The US federal Occupational Safety and Health Administration at osha.gov OSHA's mandate is to improve health and safety in the workplace by enforcing standards. Such standards encourage the use of Master Disconnect Switches (like 75920) that can be locked-out or tagged-out.

OVERCURRENT

A current greater than the rating of a device or component. Protection is usually afforded by adding a fuse or circuit breaker to protect against overcurrent.

OVERFUSING

It's what not to do! When a fuse is inserted that has a higher amperage rating higher than that which is appropriate to the circuit. In this condition, it's unlikely the fuse will blow first - a more costly pcomponent will!!!

OVERVOLTAGE

A voltage greater than the rating of a device or component.
Overcurrent and overvoltage are highly likely to damage circuit components. Many Cole Hersee brand electronic products provide protection to the entire circuit components.

Back to top 

P

PAL

A type of cartridge fuse available in various configurations: Series 0, Series 1, Series 2 and Series 3.

PANEL

A collection of circuit breakers, switches, and instrumentation installed into a panel which provides the central point for power distribution and monitoring for the electrical system. Also known as panelboard or dash or dashboard.

PARALLEL CIRCUIT

An electrical circuit in which the positive connections are all in common and the negative connections are all in common. The voltage of the system appears across each branch of the circuit. The current varies as required by each load or source.

PARALLEL DEVICE

A switch, solenoid, relay, or solid state device which is used to connect multiple batteries or busbars together.

PARASITIC LOAD

Even when some equipment is turned off, there is still a small current draw, sometimes used to maintain the settings (such as time) on electronic equipment. Even though the draw may only be milliamps, the parasitic load adds up where there are multiple devices on a vehicle that is left inactive. 
Installing an LVD would stop the starting battery from being drawn down to a level where the vehicle cannot be started.

Quiescent current is different. It  is the current draw of the device when it is turned On and ready to perform, but not actually driving a load. For example, quiescent current on a FlexMod LVD is typically 1mA.

PASCAL

PASCAL Pa The pascal is the SI unit of pressure. One pascal is the pressure generated by a force of 1 newton acting on an area of 1 square metre. It is a rather small unit as defined and is more often used as a kilopascal [kPa].

It is named after the French mathematician, physicist and philosopher Blaise Pascal (1623-62).

PICO

PICO p A metric prefix meaning one million millionth or 10^-12. Commonly used in capacitance pF.

PIEZO

Certain substances such as crystals generate a small amount of electrical charge (piezoelectricity) when pressed. The piezoelectric effect is a reversible process. Materials that generate electrical charge when pressed can also the reverse the piezoelectric effect, and generate an internal force under the effect of electricity. Piezoelectricity is found in applications such as the production and detection of sound, generation of high voltages, electronic frequency generation, microbalances, and ultrafine focusing of optical assemblies… and for everyday uses such as acting as the ignition source for cigarette lighters and push-start propane barbecues. The first practical application for piezoelectric devices was sonar, first developed in France in 1917 in an ultrasonic submarine detector. The piezoelectric effect is used in the Cole Hersee 40205 Milliamp Rocker & Alarm.

PITCH

On a screw thread, the nominal distance between two adjacent thread roots or crests.

POLE

The number of separate circuits that can be active through a switch at any one time. So a switch can be rated SP or DP (Single or double pole).

POWER

Electrical energy measured according to voltage and current (normally watts). Power in watts equals volts times amperes for DC circuits.

PRE-FUSING

Fusing high current circuits close to the battery to protect high current primary cables. Also called “Primary Fusing”. Overcurrent protection of the heavy electrical cabling has traditionally been performed by Fusible Links. There are problems with these Links - there is a possibility of causing fires; and they are time-consuming to replace, often necessitating replacement of runs of heavy cable. Littelfuse bolt-down fuses like MEGA and MIDI fuses are gradually replacing Fusible Links.

PSi

(Pounds Per Square Inch) In trucking, unit of measurement for tire air pressure, air brake system pressure and turbocharger boost.

Back to top 

Q

QUIESCENT CURRENT

Quiescent current is the current draw of a device when it is turned On and ready to perform, but not actually driving a load. For example, quiescent current on a FlexMod LVD is typically 1mA.

Parasitic load is different.
Even when some equipment is turned off, there is still a small current draw, sometimes used to maintain the settings (such as time) on electronic equipment. Even though the draw may only be milliamps, the parasitic load adds up where there are multiple devices on a vehicle that is left inactive. 
Installing an LVD would stop the starting battery from being drawn down to a level where the vehicle cannot be started.

QUIESCENT CURRENT

The small current drawn by a device when it is not actually working. It's the current drawn that keeps a device in readiness to work. It's desirable that a device has a low quiescent current. Of course, on a vehicle with a finite electrical power supply, the sum of the quiescent currents drawn by several devices can lead to a dead battery, sometimes just in overnight storage. Installation of an LVD can remove such a problem.

Back to top 

R

RECTIFIER

An electrical device used to change AC power into DC power. A battery charger is a rectifier.

RECTIFIER

A device that allows current to flow in only one direction, such as a diode. Used to convert (or rectify) AC current into DC

REEFER

Refrigerated trailer with insulated walls and a self-powered refrigeration unit. Most commonly used for transporting food.

ROADSPLASH

Dirty rainwater and slush thrown up under a vehicle. These fluids can cause damage to unprotected electrical systems. The problem is magnified when roas salt (an electrolyte) is added to the mix. It causes corrosion of the body, and of vulnerable electrical systems. The newer magnesium/calcium salts cause even more damage than the conventional sodium chloride (salt) de-icing chemicals..

RPM

(Revolutions Per Minute) Measure of the speed at which a shaft spins. Most often used to describe engine crankshaft speed. Indicated by a tachometer.

RV

Recreational Vehicle. A home on wheels. It could be simple unit on a pick-up truck, a camper trailer or a large Class 8 straight truck. Includes what was formely known a a motorhome (or a caravan in the UK).

Back to top 

S

SAE Oil Viscosity

Motor oil is a lubricant that minimizes friction between moving parts. The viscosity (‘thickness’) of the oil is specified by the vehicle manufacturer according to SAE metrics. The Society of Automotive Engineers (SAE) codes motor oils according to their viscosity characteristics - 0, 5, 10, 15, 20, 25, 30, 40, 50 or 60 (increasing viscosity). These numbers take the letter W, designating their "winter" or cold-start viscosity, at lower temperature. The viscosity is a measure of the time it takes for a standard amount of oil to flow through a standard test orifice, at standard temperatures. The longer it takes, the higher the viscosity and the SAE code. The SAE designation for multi-grade oils includes two viscosity grades; for example, 10W-30. The two numbers are individually defined by SAE J300 for single-grade oils. 10W-30 oil must pass the viscosity grade test for both 10W and 30. SAE J300 defines the viscometrics related to these grades. The SAE has a separate viscosity rating system for gear, axle, and manual transmission oils, SAE J306.

SAE STANDARDS

The Society of Automotive Engineers maintains a series of standards for all things automotive. Satandards are usually prefixed with a J, such as in standard J1455. Reputable manufacturers (such as Littelfuse CVP) manufacture their parts to meet or exceed the appropriate SAE standard.

SCHOTTKY

Schottky diode. A fast-acting semiconductor diode with a very fast switching action. Battery Isolators with Schottky diodes are mandated for emergency compartments of US ambulances.

SECOND

SECOND s The second is the basic unit of time. It is defined as the length of time taken for 9192631770 periods of vibration of the caesium-133 atom to occur.

SEMICONDUCTOR

A semiconductor is an electronic conductor with a resistivity between metals and insulators. The term 'solid state' refers to semiconductor components.

SEMITRAILER

Truck trailer supported at the rear by its own wheels and at the front by a fifth wheel mounted to a tractor or dolly.

SET SCREW

A threaded fastener typically used to hold a sleeve, collar or gear on a shaft to prevent relative motion. You can find it on several Cole Hersee brand knobs, many of which have a metal sleeve with set screw to insure reliable operation. A set screw normally does not have a head. Various socket types are provided to allow the set screw to be rotated. These types include hexagon socket, fluted socket, screwdriver slot and square head.

SFE

A type of fuse manufactured by Littelfuse and others, originally designed to specifications of the Society of Fuse engineers, All types are 1/4" in diameter, but vary in length according to amp rating.

SHIELDING

Imposing a metallic barrier to reduce the coupling of undesirable signals, such as in a shielded cable that is necessary in multiplexing, or domestically in hi-fi connectors.

SHORE POWER

AC or DC power supplied in a marina to a boat, or by extension to a truck at a truck stop. Shore power is highly desirable to mitigate truck idling.

SHORT CIRCUIT

A bad situation! It's an abnormal low resistance path between any two parts of a circuit. It will likely be accompanied, by overheating, an explosion, or fire. it's also likely to cause damage to components or equipment in that circuit. Fortunately Littelfuse is the world's largest manufacturer of circuit protection, producing thousands of different devices to keep electric circuits safe worldwide.

SI

The International System of Units that has replaced the metric system in all countries except Myanmar, Liberia and USA.

SILVER TUNGSTEN

Silver tungsten carbide is an excellent material for electrical contacts because of its ability to resist “sticking” or welding of the contacts, and because of its resistance to oxidation. Cole Hersee engineers selected silver tungsten carbide for the 200Amp solenoids 24214 and 24213 because it is a harder material than silver alone, or even silver tungsten, and is more resistant to arc erosion and contact wear.

SKIVING

A patented Littelfuse process in which the base resistive material that makes up fuses is precisely shaved in order to improve the accuracy of the range in which fuses will blow.

SLOW BLOW

A fuse that is a slow blow has a longer delay when subjected to over-current, before it fails. Slow blow fuses are required for loads that have high starting surges, like motors.

SMART BATTERY ISOLATOR

A Cole Hersee brand product consisting of a conventional solenoid plus electronic control. Items number 48525, 85A and 48530, 200A at 12V DC.

The solenoid does the heavy switching, and is controlled by the electronics. It can replace the traditional diode Battery Isolator and has several advantages over thatc type.

SOLENOID

An electromechanical device (or relay) that is used to switch large currents. It consists of a coil of wire and a moving contact that makes an electrical connection when the coil of wire is energized. Cole Hersee manufactures over 50 kinds of solenoid. See # 24059

SPDT

Single Pole, Double Throw. Circuitry which describes a switch. Single Pole means that this switch controls one circuit. Double Throw means that this switch has two On positions. It could be an On-On or an On-Off-On.

SPST

Single Pole, Single Throw. Circuitry which describes a switch. Single Pole means that this switch controls one circuit. Single Throw means that this switch has only two positions - and those are highly likely to be On and Off.

STARTING BANK

An arrangement of batteries that is dedicated to engine starting.

STRAY CURRENT

Unwanted current flows which occur due to a partial short circuit.

STRESS

An external force applied to a component or assembly that tends to damage or destroy it.

SULFATION

The highly undesirable formation or deposit of lead sulfate on the surface and in the pores of the active material of the lead plates of a battery. If the sulfation becomes excessive and forms large crystals on the plates, the battery will not operate efficiently and may not work at all. Common causes of battery sulfation are standing a long time in a discharged condition, operating at excessive temperatures, and prolonged under or over charging. surge

SURGE

A large amount of current during the initial starting phase of a motor, for example. Motors and their circuits must be designed to accept a surge without damage, and circuit protection needs to be selected to be useful, but not trip during a normal surge.

Back to top 

T

TAG-OUT

A safety precaution in which a switch is secured with a sealed tag to prevent accidental actuation. Such actions may be required by regulations such as those mandated in the US by OSHA. See 75920 Master Disconnect Switch, which can be readily locked-out or tagged-out.

TAGOUT

A safety precaution in which a switch is secured with a sealed tag to prevent accidental actuation. Such actions may be required by regulations such as those mandated in the US by OSHA. See 75920 Master Disconnect Switch, which can be readily locked-out or tagged-out.

TAP

A connection point brought out of a transformer winding to permit changing the turns ratio. Also the act of adding a wire to another, to create a second circuit. See Cole Hersee brand Quik-Tap Cable Splicers 30223.

TARP

A rugged textile (or tarpaulin) covering on top of a truck load, especially loose loads that could become windborne in transit. Tarps can be laboriously manually secured or used in efficient automatic tarping systems. Cole Hersee makes a Forward & Reverse Module 24452 that is perfect for such applications.

TERMINATION

Describes how a switch is connected to the circuit or device it activates. Termination can be via screw terminals, blades, bullets, leads, or a wide variety of connectors, plugs, and sockets.

THROW

The number of circuit paths that can be controlled by any one pole. See ST and DT (Single and Double Throw)

TIME-CURRENT

Time-Current Characteristics are important considerations when selecting the correct fuse. Readings are typically drawn as lines for each fuse amperage on a geometric graph that plots time vs current.

TIN PLATING

A plating of the element tin, which prevents corrosion. Commonly used to plate copper components such as a power busbar.

TORQUE

A measure of how much twisting needs to be applied to a fastener (such as a screw or a hexnut). The unit is expressed in force x length. The SI (metric) unit is newton meters (Nm); in inch measurement, pound foot (lb-ft) or pound inch (lb-in) is used.

TORQUE

A rotational moment; it is a measure of how much twisting is applied to a fastener. The units used to measure torque are in the form of force times length, usually measured in Newton-metres (Nm) if metric units are used, or pounds feet (lb-ft) when imperial units are used.

TORQUE WRENCH

A manual wrench which incorporates a gauge or other method to indicate the amount of torque transferred to the nut or bolt. Use of a torque wrench is recommended in order to ensure secure fastening on the one hand, or over-torquing on the other.

TRACTOR

Truck designed primarily to pull a semitrailer by means of a fifth wheel mounted over the rear axle(s). Sometimes called a truck tractor or highway tractor to differentiate from it from a farm tractor.

TRANSDUCER

A device that takes one form of energy and converts it to another: sound to electric (microphone), electric to sound (speaker), electricity to heat (resistive heater), electricity to light (lamp), light to electricity/electronic (photoelectric cell) etc.

TRUCK WIRING

Heavy-duty wiring systems are designed to carry specific amounts of current, at a voltage of usually 12V and a maximum of 13.5V. With trailers and combination vehicles there should be no more than a 0.7V drop per trailer when measured at the rear trailer lamps. 24V and higher voltage systems are becoming commoner.

For a 12V system the wiring should be capable of providing a minimum of 10V to any incandescent lamp on a straight truck or a combination. Voltage drop is the primary consideration in selecting the appropriate wire size. The length of wire is a major contributing factor contributing to voltage drop.

Although wiring colors are not standardized in tractor units, there is a color standard for trailers:

White wire Ground return to the tractor

Black wire Clearance, side marker and license plate lamps

Yellow wire Left-hand turn signal and hazard signal lamps

Red wire Stop lamps and ABS

Green wire Right-hand turn signal and hazard signal lamps

Brown wire Tail, clearance, side marker lamps, identification lamps

Blue wire Auxiliary circuits

Back to top 

U

UL

Abbreviation for Underwriters Laboratories, a US rating organization. Approved devices (such as many Cole Hersee switches) carry the UL label.

UNDERFUSING

Sometimes referred to as a nuisance blow. The condition where a fuse is inserted with a rating that's too much lower than that of the circuit. underfusing almost guarantees that a fuse will blow repeatedly, even though the circuit is functioning normally.

UNIVERSAL

In the switches context, UNIVERSAL equates to multi-purpose, rather than some of our specialized switches which are generally used for one purpose.

UPFITTER

Upfitter A company that specializes in the addition of equipment on a vehicle, that was not installed by the manufacturer. Many of these shops are specialists, such as police fleet upfitters who take a standard car and add computer consoles, extra lights, GPS, gunracks, emergency tool bins and the like. Such police fleet upfitters may customize according to the specs of different municipal or state fleets.

USCG

United States Coast Guard controls boating in US waters and issues safety regulations for boaters such as 183.410 for ignition protection.

Back to top 

V

V DC

Volts of direct current, as opposed to V AC.

VIN

(Vehicle Identification Number)
Assigned by the manufacturer, this number is unique to each vehicle and appears on the vehicle's registration and title.

VOLT

The unit of voltage or potential difference. One volt is the difference of potential between two points of an electrical conductor when a current of 1 ampere flowing between those points dissipates a power of 1 watt.

It is named after the Italian physicist Count Alessandro Giuseppe Anastasio Volta (1745-1827).

VOLTAGE

Electrical pressure, the force that causes current to flow through a conductor. Voltage must be expressed as a difference of potential between two points since it is a relational term. Connecting both voltmeter leads to the same point will show no voltage present although the voltage between that point and ground may be thousands of volts.

Calculations often involve Ohm's Law, q.v.

VSRT

Voltage Sensing Relay & Timer #48541. A FlexMod module that monitors and controls timing and vehicle voltage. Conserves battery voltage by automatically shedding auxiliary loads when voltage is low; automatically restoring connections when voltage is back to normal. Available as a dealer-programmable unit #48741

Back to top 

W

WATT

WATT W The watt is used to measure power or the rate of doing work. One watt is a power of 1 joule per second.

It is named after the Scottish engineer James Watt (1736-1819).

WINCH

A device used for hauling a rope or cable, and having a drum on which the cable is wound. The winding mechanism may be a hand-crank or a motor. The term 'windlass' is generally preferrred in nautical usage. A motorized winch (or windlass) will generally need a specialized forward/reverse switch or a control unit such as the 24452.

WINDLASS

A winch. The term is especially used on boats, and refers to a hand-cranked mechanism or a motor-powered type. A motorized windlass (or winch) will need the use of some kind of forward and reverse switch or a forward and reverse control such as 24452. The word 'windlass' derives from 'winding-beam' - envisage the horizontal rotating beam above a well that winds the rope that raises a bucket.

WIPING CONTACTS

Wiping action contacts slide against each other when opening or closing a circuit. This action helps clean the contacts of contamination and keeps contact resistance low.

WORK TRUCK

Any truck used in a working situation, but excluding Class 8 (big trucks). Typically though, it refers to light to medium trucks that may be used by contractors or fleets. So a small flatbed truck may be driven for domestic use, but when it is fitted with semi-permanent toolchests or power equipment, it becomes a ‘work truck’. The premier tradeshow in the US for this market is the annual Work Truck Show.

WTS

The Work Truck Show. An important annual tradeshow organized by the NTEA (National Truck Equipment Association).

Back to top 

X

Back to top 

Y

Back to top 

Z

Z

Z is for zepto. You didn't study the Metric Prefixes?

Back to top