Glossary of Car Audio Terminology.
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AC (Alternating Current)— Energy, which alternates back and forth at a certain frequency. The frequency is measured in Hertz. In automobiles, AC is produced by the alternator and then rectified to DC.
Acoustical Energy —Energy consisting of fluctuating waves of pressure called sound waves.
Acoustics— A science dealing with the production, effects, and transmission of sound waves through various mediums.
Acid— The term normally used to refer to the fluid found in a vehicle storage battery. This fluid is a somewhat diluted form of sulfuric acid. The chemical reaction between the lead of the battery's plates and the sulfuric acid creates and stores electricity. (Also see Electrolyte.)
Active Arming— A method for arming a security system that requires some action on behalf of the driver/operator. This action could include pressing a button on a remote transmitter or entering a code on a keypad.
Air Horns— A type of horn that uses compressed air instead of an electrical diaphragm or voice coil to produce sound. These horns are usually driven by an electric air pump that receives its trigger from a host security system.
Alarm Reset— The property of an alarm system which resets the alarm to an armed state after is has sounded for a predetermined period of time. (Also see Reset.)
Alarm Retriggering— A condition that occurs in a security system where once it has been triggered, instead of sounding the siren for its designated time interval, it is retriggered and made to sound again.
Alternator— A mechanically-driven automotive device that generates DC power and is the primary source of vehicle power.
Alternator Whine— A siren-like whining that appears when the RPMs of the engine increase. The noise is usually the result of a voltage differential created by more than one ground path or poor ground path.
Ambience Synthesizer— A unit that produces an artificial ambience pattern; one that is used to create the impression of the listener and/or performer being in a particular performance space.
Amplification— An increase in a signal level, amplitude, or magnitude.
AM— See Amplitude Modulation.
Ammeter— An instrument used for measuring the amount of current flowing in a circuit.
Amperage— A unit of electrical current. The force through which the energy is pushed through a conductor. Measured in amps; Ohm's Law symbol is l.
Ampere— The unit of measurement used to determine the quantity of electricity flowing through a circuit. One ampere flows through a 1 Ohm resistance when a potential 1 Volt is applied.
Amplitude— The measure of how powerful sound waves are in terms of pressure.
Amplitude Modulation (AM)— A method of modulation in which the amplitude of the carrier voltage is varied in proportion to the changing frequency value of an applied (audio) voltage. (Also see Frequency Modulation.)
Analog— An electrical signal in which the frequency and level vary continuously in direct relationship to the original acoustical sound waves. Analog may also refer to a control or circuit, which continuously changes the level of a signal in a direct relationship to the control setting.
Analog Switch— A hardware-oriented switch that only passes signals that are faithful analogs of transducer parameters.
Anode— The electrically positive pole of an electronic device such as a semiconductor. A diode, for instance, has a positive and negative pole; these are known as the anode and the cathode.
Antenna— A mechanical device, such as a rod or wire, which picks up a received signal or radiates a transmitted signal.
Arm— The term used to describe the act of causing a security system to reach a state in which it will protect the vehicle.
Arming Delay— A term used to describe the elapsed time between the moment a security system is first told to arm, and when it is actually armed. This normally only applies to systems that are passively armed, but can apply to actively armed systems as well. (Also see Exit Delay.)
Attenuate— To lessen the amount of force, magnitude, or value of something.
Audio Frequency Spectrum— The band of frequencies extending roughly from 20 Hz to 20 kHz.
Audio Oscillator— A device that produces tones at specific frequencies for testing either equipment or entire systems.
Audio Signal— An electrical representation of a sound wave in the form of alternating current (AC) or voltage.
Auto Reset— The ability of a security system to automatically reset itself after being triggered. (Also see Alarm Reset and Reset.)
Back-up Battery— A separate battery added to the security system as an alternate power supply to serve as a backup in case a thief should disable the vehicle's main battery. Back-up batteries are typically the lead-acid gel cell type and are most effective when hidden from detection.
Ballast Wire— The name given to a special resistance wire used between the ignition switch and the engine's high voltage coil. This wire is typically composed of a carbon compound instead of normal copper.
Bandpass Filter— In mobile electronics, a device, which incorporates both high-pass, and low-pass filters in order to limit and attenuate both ends of the frequency range.
Bandwidth— Refers to the “space” in the frequency response of a device through which audio signals can pass (between lower and upper frequency limits, those points where the signal level has rolled off 3 dB).
Bass— The low audio frequency range, normally considered to be below 500 Hz.
Bass Reflex— A vented enclosure that allows control of rear radiated sound waves.
Battery— A device, which manufactures electrical energy. A battery makes direct current through a collection of cells.
Bias— An unbalanced sound level.
Boomy— Usually refers to excessive bass response, or a peak in the bass response of a recording, playback or sound reinforcement system.
Brain— The common term used to refer to the main control unit of a security system. (Also see Control Unit.)
Butterworth Filter— A filter with a pass-band with no ripple but usually sacrifices some steepness in attenuation.
Capacitance— The property exhibited by two conductors separated by a dielectric, where an electric charge becomes stored between the conductors. (Also see Farad.)
Capacitor— An electronic device which stores energy and releases it when needed. Also used to direct high frequency energy to tweeters. Rated in Farads.
Cathode— The electrically negative pole of an electronic device such as a semiconductor.
Cell— A single unit for producing DC electricity by electrochemical or biochemical action. A common vehicle battery is composed of a number of individual cells connected together. Each cell is typically rated at 2.11 Volts each, and a common 12VDC automotive battery is composed of 6 separate, 2 Volt cells. (Also see Battery.)
Channel (Security)— The term usually used to describe the number of different functions possible for manipulating the buttons on a remote control transmitter.
Chassis— The metal frame of the vehicle.
Chebyshev Filter— A filter that has some ripple in the pass-band but has an initial attenuation slope, which is steeper than a Butterworth filter.
Chirp— The term used to describe the brief sounding of a security system's siren designed to indicate the stat of arm of the system.
Circuit— A closed path through which current flows from a generator, through various components, and back to the generator.
Circuit Breaker— An electromechanical device designed to quickly break its electrical connection should a short circuit or overload occur. A circuit breaker is similar to a fuse, except it will reset itself or can be manually reset, and will again conduct electricity.
Clipping— The distortion that occurs when a power amplifier is overdriven. This can be seen visually on an oscilloscope, when the peaks of a waveform are flattened, or “clipped off,” at the signal's ceiling.
Closed Circuit— A continuous unbroken circuit in which current can flow without interruption. Also known as a closed loop.
Closed Loop— A feedback path in a self-regulating control system. Unlike a standard open state trigger that needs to have a connection established to serve as a trigger, a closed loop trigger will act to trigger a security system when its loop (connection) is broken.
Closure Wire— The name given to describe a wire found on some vehicles that, when given a certain duration input, will cause that doors to lock and the windows/sunroof to close.
Code— The aspect of a security system that can be tailored be the manufacturer or the installer to personalize the particular system for a user or group of users. A remote security system that is coded will operate only with those transmitters that are coded to the same matching code.
Coaxial Speaker— A coaxial speaker has a large cone for the low range, and a smaller tweeter for the high spectrum. There is a cross-over network which divides and routes the signal to the correct driver.
Co-Linear Antenna— An antenna that uses a phasing coil to electrically connect stacked elements in the proper phase relationship.
Compliance— The measurement in liters or cubic feet of the volume of air that is equal to the compliance of a speaker's total suspension.
Cone— The most common shape for the radiating surface of a loudspeaker. Often used to refer to that part of the speaker that actually moves the air.
Constant Output— An output of a security system that provides a constant or continuous output to drive a device. Often used for sirens and engine interrupts.
Control Unit— The central processor for a security system. (Also see Brain.)
Coulomb— An amount of electrical charge, which contains 6.24 X 10 of electrons.
Crossover— A device intended to separate the different frequency bands and redirect them to different components.
Crossover Frequencies— The frequencies at which a passive or electronic crossover network divides the audio signals, which are then routed to the appropriate speakers.
Crossover Network— A unit, which divides the audio spectrum into two or more frequency bands. (Also see Crossover Frequencies.)
Current— The rate of electrical or electron flow through a conductor between objects of opposite charge. Symbol l, measured in amperes or amps.
Current-fed Antenna— An antenna in which the feeder or transmission line is attached to the radiator at a current loop. This type of antenna requires a ground plane.
Current Sensing— A name given to a form of alarm system trigger that relies on sensing a change in the power supply of the vehicle. More accurately called voltage sensing, this feature is found on many inexpensive alarm systems. (Also see Voltage Sensing.)Damping— The reduction on the magnitude of resonance by the use of some type of material.
DAT— Digital Audio Tape.
DC— Direct Current. A flow of electrons, which travels in one direction only.
Decibel (dB)— The standard unit of measurement used to indicate the relative intensity of sound.
Dedicated Fuse— A fuse designated to supply power and protection for one particular circuit only.
Destructive Interference— A phenomenon that occurs when speakers are 180 degrees out of phase, i.e., what one speaker is trying to produce, the other speaker is fighting to cancel. One speaker's wave is in the positive phase (rarefaction), while the other speaker's wave is in the negative phase (compression).
Diaphragm— A thin metal or dielectric disk used as the vibrating member in loudspeakers. Also known as a cone.
Difference of Potential— The algebraic sum of voltages at two points of different electrical potential.
Diode— A two-electrode (two-terminal) device, which allows a voltage/signal to pass through it in one direction only.
DIN— German industrial standards, which are used in many European countries. DIN size refers to the stereo size that fits most European cars.
Disarm— The opposite of arm, or the term used to describe the action of placing a security system in an inactive or standby mode. (Also see Arm.)
Distortion— Sound that is modified or changed in some way. In a speaker, distortion is produced by several things, most related to poor construction. Voice coil rubbing (caused by being overdriven) is the most common cause of distortion.
DMM— Digital Multimeter. A digital meter that gives a precise reading of voltage, current, or ohms. This type of meter “samples” the input and feeds it to a digital readout.
Dome Light— The common term used to describe the overhead (or headliner) mounted interior courtesy light.
Door Lock Solenoid— The proper name for the electric bi-directional actuator used to provide powered control of vehicle door locks. Also called a Door Lock Actuator.
Doppler Sensor— Another name for a spatial type sensor, also commonly called radar sensors. (Also see Spatial Sensors.)
DPDT— Double Pole Double Throw. A term used to describe a relay that has two separate poles or contacts and can throw or make electrical contact with two separate stationary contacts.
Dress— The arrangement of signal leads and wiring for optimum circuit operation, cosmetic appeal, and protective routing.
Driver— Another term for a loudspeaker. Often used when the loudspeaker is coupled to a horn for acoustic coupling and controlled dispersion of sound.
DSP— Digital Signal Processing (or Processor). A type of processing accomplished by a microcomputer chip specifically designed for signal manipulation, or a component using such processing. The term is often misused as a synonym for ambience synthesizer; however, DSP can do much more than sound field creation.
DTMF— Dual Tone Multi-Frequency.
Duty Cycle— An engineering term used to describe the actual time (or frequency) that a circuit or device operates. A pulsing alarm output that is on for seven-tenths of a second and off for three-tenths of a second would have a 70% duty cycle.
Dynamic Range— The range difference between the quietest and the loudest passages of the musical selection or program signal being played.
Efficiency— The measure of loudspeaker's ability to convert power to work. Formula: Efficiency=(power out/power in) x 100. Efficiency is always expressed as a percentage.
Electrolyte— The name for the mixture of diluted sulfuric acid found in standard lead-acid vehicle storage batteries. (Also see Acid)
Electrolytic Capacitor— A capacitor with a negative and a positive terminal that only passes alternating current.
Emergency Override— A button or switch, possibly separate or hidden from commonly used controls of a security system, that is used specifically to override or disarm a security system in the event that the primary means is unavailable or disabled.
EMR Detector— A tool used to find the source of low frequency tape head interference (electromagnetic radiation.)
Engine Disable— A means, either electrical or mechanical, designed to prevent the vehicle's engine from either starting or running. The most common variety of engine disable uses a simple automotive relay to inhibit either the starter or the ignition.
Entry Delay— The time interval a security system waits before sounding the alarm after a door of the vehicle has been opened.
Exit Delay— The name given to the time interval a security system waits once given a command to arm. Exit delays are usually found on non-remote security systems that rely on keypads or the ignition switch to arm. This delay gives the operator time to exit the vehicle before the system arms.
Farad (F)— The basic unit of a capacitance. A capacitor has a capacitance of 1F when a charge of 1 Volt across the capacitor produces a current of 1 Ampere through it. Named after Michael Faraday.
FCC— Federal Communications Commission. The U.S. government agency which oversees and regulates electronic communications.
Fidelity— A term used to describe the accuracy of recording, reproduction, or general quality of audio processing.
Flashing Lights— A term used to describe the interfacing of the vehicle's parking lights, dome light, emergency lights, etc., with a security system so that the lights flash by the system.
Flat Response— An output signal in which fundamental frequencies and harmonics are in the same proportion as those of the input signal being amplified. A flat frequency response would exhibit relatively equal response to all fixed-point frequencies within a given spectrum.
Fletcher-Munson Curves— A set of curves that depict the uneven frequency response of human hearing.
FM— See Frequency Modulation.
Free Air Resonance— The frequency at which a speaker will naturally resonate.
Frequency— The term in physics that refers to a number of vibrations or cycles that occur within a given time.
Frequency Counter— A device that assists in speaker parameter testing, as well as identifying the frequency of specific tones.
Frequency Modulation (FM)— A method of modulation in which the frequency of the carrier voltage is varied with the frequency of the modulating voltage. (Also see Amplitude Modulation.)
Frequency Response— A term which describes the relationship between a device's input and output with regard to signal frequency and amplitude.
Fuse— A device designed to provide protection for a given circuit or device by physically opening the circuit. Fuses are rated by their amperage and are designed to blow or open when the current being drawn through it exceeds its designed rating.
Fusible Link— Designed to perform the same task as a fuse, but resembles a wire. Fusible links are commonly used in ignition switches and other high current circuits.Gain— Refers to the degree of signal amplification.
Generator— A rotating machine that produces DC electricity. Also and electronic device used for converting DC voltage into AC of a given frequency and wave shape.
Glass Sensor— A device designed to detect the sound of breaking glass or metal-to-glass contact, thus triggering a security system. Also called Sound Sensors, Glass Breakage Sensors, or Sound Discriminators.
Ground— The term given to anything having an electrical potential of zero. Most modern vehicles are designed around a negative ground system, with the metal frame being the vehicle's ground.
Ground Loop— The term given to the conduction that occurs when a voltage potential exists between two separate ground points.Harmonic— A weaker overtone or undertone of the original note responsible for the character of the note.
Harness— The universal name for a bundle or loom of wires that compose the wiring for a system.
Hertz (Hz)— The unit of frequency within a specific period, such as alternating or pulsating current; 1 Hz = 1 cycle per second.
High Frequency— Refers to radio frequencies in the 3-30 MHz band. In audio it usually refers to frequencies in the 5-10 kHz band.
High Pass Filter— A network of components, which attenuate all frequencies below, a predetermined frequency selected by the designer. Frequencies above cut-off are passed without any effect.
Horn (Audio)— Refers to a loading device when part of a bass enclosure, or a directional device when used with a high frequency driver or compression driver.
Horn (Security)— Refers to the built-in factory horn in the vehicle. Factory horns can be of the diaphragm type, voice coil type, or air-pump driven type (air horn). All types of horns are capable of being interfaced to a security system.Ignition Kill— A device designed to prevent the vehicle's ignition circuit from operating. An ignition kill device can work by either interrupting one or both of the primary wires leading to the ignition coil or by shorting out (grounding) the ignition coil's positive primary wire. Also called an Ignition Disable.
Ignition Power— Refers to a source of power in the vehicle, controlled by the ignition switch that has +12VDC on it when the ignition key in both in the run and start positions.
Imaging— The presence of sound stage with a perceived openness.
Impact Sensor— A sensor designed to detect various degrees of impact or vibration applied to the vehicle and then produces an output to trigger a security system.
Impedance (Audio)— A measurement of the resistance to the audio current by the voice coil of the speaker. (Also see Nominal Impedance.)
Impedance (Electrical)— The total opposition offered by a device or circuit to the flow of alternative current.
Inductive Coupling— Radiated noise that is transmitted through a magnetic field to surrounding lines.
Inductor— An electrical component in which impedance increases as the frequency of the AC decreases. Also known as coils that are used in passive crossovers. Inductors are rated in Henries.
Infinite Baffle— A loudspeaker baffle of infinite space that has no openings for the passage of sound from the front to the back of the speaker. Also, a sealed enclosure where the internal volume is greater than the Vas of the driver.
Infrared Sensor— A type of spatial sensor that uses infrared energy to detect an object (a hand, arm, or body) entering a protected area. (Also see Spatial Sensors.)
Input (Audio)— The high level (speaker) or line level (RCA) signal connections that run into one component from another system component.
Input (Security)— Any wire on a security system designed to accept a signal from some outside source such as the vehicle's wiring. Door trigger, hood trigger, trunk trigger, and sensor trigger wires are all inputs.
Instant Trigger— The term used to describe any trigger input on a security system that is designed to cause the system to respond instantly when triggered.
Integrity— The expected durability of a component or connection.Joule— A unit of energy equal to one watt per second.
Jump— To provide a temporary circuit around a component or other circuit.Keypad— A panel usually made of metal or plastic with numbered push-buttons (like a touch-tone telephone) designed to provide access to certain types of security or cellular systems.
Kirchoff's Current Law (KCL)— A law stating that the total current entering a point or junction in a circuit must equal the sum of the current leaving that point or junction.
Kirchoff's Voltage Law (KVL)— A law stating that the voltage supplied to a DC circuit must equal the sum of the voltage drops within the circuit.
KHz— Abbreviation for kilohertz, or 1000 cycles per second.Last Door Arming— A feature found on some security systems that enables the system to suspend itself from arming until the last door on the vehicle has been secured.
LCD— Liquid Crystal Display.
LED(s)— Light Emitting Diodes. A form of diode that sheds light. Used in many systems for indicator purposes.
Loudspeaker— An electro-acoustic transducer that converts electrical audio signals at its input to audible sound waves at its output.
Low Frequency— Refers to radio frequencies within the 30-300 kHz band. In audio it usually refers to frequencies in the 40-160 Hz band.
Low Pass Filter— A network of components which attenuate all frequencies above a predetermined frequency selected by the designer. Frequencies below cut-off are passed without any effect.Magnet— A device which has the ability to attract or repel pieces of iron or other magnetic material. Speaker magnets provide a stationary magnetic field so that when the coil produces magnetic energy, it is either repelled or attracted by the stationary magnet.
Memory— The work most commonly used to refer to a system's ability to retain specific information.
Microprocessor— A semiconductor that can be programmed to perform a variety of tasks in many different systems.
Midrange Driver— A loudspeaker specifically designed to reproduce the frequency in the middle of the audible bandwidth. Most musical energy lies in the midband.
Milliamps— A unit of measurement of electric current equal to 1/1000 th of an ampere. The milliampere is the most common unit used when measuring quiescent current drain.
Module— A term commonly used to describe a self-contained part or device that can perform a specific function.
Motion Sensor— A sensor specifically designed to detect a gentle or sharp up and down or side-to-side motion of the vehicle.
Multimeter— A common term used to describe a VOM. A multimeter usually has the ability to measure volts, ohms, and amperes or milliamperes.
Negative Door Switches— A common type of switch found on most modern vehicles, which provides the trigger for the factory interior lights, key buzzer, factory alarm, etc.
Negative Lead— The lead or line connected to the negative terminal of a current, voltage, or power source.
Normally Closed— Refers to the electrical state in which a switch may rest. Its contacts are held together or closed so that current is allowed to flow through its contacts.
Normally Open— Refers to the electrical state in which a switch may rest. Its contacts are held apart or open so that no current flows through its contacts.
Nominal Impedance— The minimum impedance a loudspeaker presents to an amplifier, directly related to the power the speaker can extract from the amplifier.Octave— A musical interval between two tones formed when the ratio between the frequencies of the tone is 2:1.
Ohm— The unit of measurement for electrical resistance.
Ohm's Law— The statement of the relationship between current, voltage, and resistance. Where I = Current, E = Voltage, and R = Resistance, I = E/R, E = IR, and R = E/I.
Open Circuit— A circuit containing a switch, filament, voice coil, etc., which is not intact and current cannot flow through.
Oscillator— A device, which produces an alternating current or pulsating current or voltage electronically. (Also see Audio Oscillator.)
OSHA— Occupational Safety and Health Administration. The government agency, which regulates workplace safety and health.
Output (Audio)— The high level (speaker) or line level (RCA) signals sent from one system component to another, or the high level signal from an amplifier to the system speakers.
Output (Security)— Any wire on a security system designed to produce a signal intended to be wired to some outside circuit or device. A siren wire, flashing light wire, and door lock wires are all outputs.
Override Switch— A switch that provides a secondary means to disarm or override a security system in the event the primary means is unavailable. (Also see Emergency Override.)
Pain Generator(s)— A name given to a type of siren that is specifically designed to produce a sound of the proper volume and pitch so as to cause physical pain to a thief's ears.
Panic— The name given to the feature of a security system that provides the ability for the operator to cause the system's siren to sound at will. The panic feature is typically initiated either by pressing a button or buttons on the remote control transmitter or by keypad command or by push-button or toggle switch.Parallel Wiring— A circuit in which two or more devices are connected to the same source of voltage, sharing a common positive and negative point, so that each device receives the full-applied voltage.
Passive Arming— The ability of some security systems to arm without requiring any direct action from the operator of the vehicle. Passive arming is usually accomplished when the operator exits the vehicle in the normal fashion. (Also see Last Door Arming.)
Passive Crossover— In mobile electronics, a simple network designed to pass high level signals and separate the frequency bands. It is also referred to as a device containing a capacitor which will send only the highs to the tweeter in a two-way (coaxial) system.
Peak— An emphasis over a frequency range not greater than one octave.
Period— The amount of time required for a single cycle of sound wave.
Phase Shift— Frequency interaction in the crossover region of passive crossovers, which can cause some frequencies to be delayed with respect to other frequencies.
Piezo— The name usually given to piezo electric drivers. This type of driver has no voice coil or magnetic assembly. Instead, piezo electric material expands and contracts when voltage is applied. The material vibrates and either radiates sound directly, or drives a diaphragm. They can only be used effectively on high frequencies.
Piezo Sensors— A type of shock or impact sensor that utilizes the properties of the piezo electric effect inherent in some materials. A Piezo Sensor typically uses a piezo electric element to sense impacts or vibrations applied to the vehicle.
Pinswitch— A simple spring-loaded mechanical switch used in many different vehicles designed to turn on interior lights when doors are opened. Pinswitches are also used in the installation of most security systems in the hood or trunk/hatch as a means of triggering the system should these points be opened.
Point of Entry— The term normally used to describe the doors, hood, trunk/hatch, windows, sunroof or any other point through which a thief can gain entry into a vehicle.
Polarity— In electricity, refers to the condition of being either positive or negative.
Polarity Reversal— A DPDT switch connected between a pair of DC input terminals so that the polarity of a pair of output terminals can be reversed or switched.
Positive Lead— The lead or line connected to the positive terminal of a current, voltage, or power source.
Potentiometer— A variable resistor made with either carbon or wire wound material, which attenuates a signal.
Power— The amount of energy (in joules) that a device delivers or consumes divided by the time (in seconds) that the device is operating.
Power Door Locks— The feature where the door locking and unlocking of the vehicle is performed by some mechanical means other than human power. Power door locks may be electric, vacuum, electro/vacuum, or a combination of both.
Power Line Noise— A varying AC ripple that is found riding on a DC voltage. It is recognized by a whining that varies with engine speed.
Power Windows— The feature where the opening and closing of the vehicle's windows is performed by some mechanical means other than human power. Power windows are typically operated by electric motors.
Pre-Amp— A circuit unit, which takes a small signal and amplifies it sufficiently to be fed into the power amplifier for further amplification. A pre-amp includes all of the controls for regulating tone, volume, and channel balance.
Proximity Sensor— A common term for a spatial type sensor that can be either the radar, ultrasonic, or infrared type. (Also see Spatial Sensor.)
Pulsed Output— An output of a security system, usually used to flash parking lights or honk horns, that is pulsed or turned on and off by the security system.
Quiescent Current— The term given to describe the amount of current consumed by a circuit when it is not performing any work (sometimes referred to as standby current.)
Qtc— The measurement of a speaker and enclosure working together as one.
Qts— The measurement of the speaker as a motor taking into consideration all mechanical and electrical losses.Radar Sensor— A common name for a type of spatial sensor.
Range (Audio)— Usually described as frequency range, this is a system's frequency transmission limits, beyond which the frequency is attenuated below a specified tolerance. Also, the frequency band or bands within which a receiver or component is designed to operate.
Range (Security)— The term used to quantify the maximum operating distance that can exist between a vehicle and the remote control transmitter. Range is usually expressed in feet or yards.
Rarefaction— A state or region of minimum pressure in a medium traversed by compress ional waves (sound waves).
Receiver— A device designed to receive a signal or command from a source such as a transmitter.
Relay— An electromagnetic switch that allows small, relatively low level signals to operate higher amperage devices. Also used when polarity reversal is necessary.
Remote— A common name for the remote control transmitter used with a remote security system. (Also see Transmitter.)
Remote Start— The feature where a security system of accessory module allows the vehicle operator to start the engine of a vehicle using a remote transmitter without actually being inside the vehicle.
Reset— The ability of a security system to automatically stop sounding the siren and return to an armed state after being triggered, as long as no further trigger conditions are present.
Resistance— The electrical term used to describe the property that various materials possess to restrict or inhibit the flow of electricity. Electrical resistance is relatively low in most metals and relatively high in most nonmetallic substances. Electrical resistance is measured in ohms.
Resonance— The term used to describe the tendency of objects to vibrate at certain frequencies. This can be a useful or undesirable effect, as in planned enclosure or driver resonance, or as in unplanned enclosure resonance or wall resonance.
Retriggering— See Alarm Retriggering.
RF— Radio Frequency. An AC frequency which is higher than the highest audio frequency.
Ripple— The deviation from a flat response in the passband.
RMS— Root Mean Square.
Roll-Off— Relates to the attenuation of frequencies, above or below a given point, at a specific rate.
Roof-Mount Antenna— A permanently-installed antenna located in the center of the vehicle's roof.
Scanning— The popular term given to the process a thief uses to break into a remote security system by quickly and sequentially transmitting all the possible security codes of a victim's security system.
Seat Sensor— A pressure activated switch designed specifically for use in detecting any pressure applied to a vehicle's seat.
Sensitivity— The rating of a loudspeaker that indicates the level of sound intensity that the speaker produces (in dB) at a distance of one meter when it receives one watt of input power.
Sensor— A device designed to detect or sense an intrusion or attack upon a vehicle by monitoring such things as motion, vibration, impact, sound, or the presence of a foreign mass.
Sensor Bypass— The ability of a security system to automatically or manually delete or bypass the triggers from all or some of the sensors tied into the security system.
Shock Sensor— A sensor that is specifically designed to detect a shock or impact applied to the vehicle.
Short Circuit— The condition that occurs when a circuit path is created between the positive and negative poles of a battery, power supply, or circuit. A short circuit will bypass any resistance in a circuit and cause it not to operate.
Signal-to-Noise Ratio— A ratio, which indicates how much audio signal there is in relation to noise, or a specified noise floor.
Siren— Any device, mechanical or electronic, that is designed to produce a loud warning sound when triggered by a security system.
Sound— A type of physical kinetic energy called acoustical energy. (Also see Acoustical Energy.)
Sound Discriminator— A device designed to listen to, evaluate, and discriminate between the sound that may be heard within the interior of a vehicle, and then trigger the security system should the sound fit within the parameters of what the sensor is designed to react.
Sound Pressure Level (SPL)— An acoustic measurement for the ratios of sound energy. Rated in decibels (SPL dBA, SPL dBC).
Sound Waves— Fluctuating waves of pressure that travel through a physical medium such as air. An acoustic wave consists of a traveling vibration of alternate compressions and rarefactions, whereby sound is transmitted through air or other media.
Spatial Sensors— Devices specifically designed to detect intrusions into or around the vehicle by monitoring the space in and around the vehicle for intruders. These sensors work on a variety of different principles, including ultrasonics, radar, radio frequency, or infrared.
SPDT— Single Pole Double Throw. A relay that has only one pole or contact but whose contact can throw or make electrical contact with two separate stationary contacts. This is the most commonly used relay in the mobile electronics industry.
Spider— A flat, round, springy device that holds the vibrating cone of a dynamic loudspeaker. The spider is where the diaphragm meets the voice coil.
SPST— Single Pole Single Throw. A relay that has only one pole or contact and can only throw or make electrical contact with one stationary contact.
Starter Disable— Any circuit or device used alone or in conjunction with a security system that is designed to prevent the vehicle's starter from operating.
Status— The state that a system is in at any given time.
Subwoofer— A loudspeaker made specifically to reproduce the lowest of audio frequencies, approximately between 45 Hz and 125 Hz.
Switch— A switch is any form of mechanical, electronic, electromechanical, magnetic, or mercury device that either opens or closes a circuit.
Switch Sensing— Switch sensing refers to the inputs on a security system designed to detect a switch closure from such triggers as a door, hood, or trunk/hatch pinswitches.
System Reset— See Reset and Alarm Reset.
Transceiver— A combination radio transmitter/receiver usually installed in a single housing and sharing some components.
Transducer— Any device, which converts energy from one form to another, i.e., electrical to acoustic or vice-versa. Loudspeakers and microphones are two types of transducers.
Transistor— An active (commonly three terminal) solid-state device in which a larger output current is obtained by small changes in the input current.
Trigger— The common name for any type of stimulus that will cause a security system to produce an alarm. A trigger could come from a pinswitch, a sensor, or a direct command from a transmitter or accessory button.
Trunk Release— The ability of a system to release the latch of the trunk/hatch by remote control.
Tweeter— A small loudspeaker or driver meant to reproduce treble frequencies.Ultrasonic Sensor— A form of spatial sensor that is designed to detect an intrusion into a vehicle by monitoring the space within the vehicle with ultrasonic energy.
Unfused Wire— Any section of wire between the power supply and a load that does not include the protection of a fuse or circuit breaker.Valet— A word used to describe the state in which a security system may be placed in which it would be prevented from arming passively and/or actively.
Valet Switch— The switch designed to provide the control to place the security system into or bring the system out of the valet state.
Vas— Compliance. A measurement in liters or cubic feet of the volume of air that is equal to the compliance of the speaker's total suspension.
Voice Coil— A coil of wire that takes in the electrical energy coming from the amplifier and converts it into acoustic energy or mechanical motion.
Voltage— The electrical pressure produced to do work.
Voltage Drop— The amount of energy consumed when a device has resistance in its circuit. The voltage (E) set up across a resistance (R) carrying a current (I). E = IR. (Also see Current Sensing.)
Voltage-fed Antenna— An antenna in which the feeder is attached to the radiator at a voltage loop. This type of antenna does not require a ground plane.
Voltage Sensing— A name given to a form of alarm system trigger that relies on sensing a change in the voltage of the vehicle. (Also see Current Sensing.)
Volt— The term used to refer to the property of electrical pressure through a circuit. The basic practical unit of difference of potential.
VSWR— Voltage Standing Wave Radio. In a standing wave system, the ratio of the voltage of the incident wave to the voltage of the reflected wave.
VOM— Volt-Ohm-Meter, sometimes called a Volt-Ohm-Milliammeter. A multimeter that measures voltage, ohms, and milliamperes.Watt— The basic practical unit of measure for electrical or acoustical power.
Wattage— Electrical power.
Wave— A single oscillation in matter (i.e., a sound wave). Waves move outward from a point of disturbance, propagate through a medium, and grow weaker as they travel farther. Wave motion is associated with mechanical vibration, sound, heat, light, etc.
Waveform— The shape of a wave.
Wavelength— The length of distance a single cycle or complete sound wave travels.
Window-Clip Glass-Mount Antenna— A nonpermanently installed antenna used in cellular applications.
Window Roll-Up— The term used for the feature that causes the window(s) on a vehicle to close upon arming, or open and close as part or a convenience feature of a security system.
Woofer— A large dynamic loudspeaker that is well suited for reproducing bass frequencies.Xmax— The distance a speaker cone can travel before the magnet loses control over the voice coil.
Zero Output— The absence of output signal or output power.
Zone— The specific area of the security system's converge or a term used to describe a specific trigger input.