Head-Units

•	Head-Unit Technical name given to the car radio unit. In Europe, we use the standard size of car stereo unit known as 'DIN'.
•	Auto Blank Skip Often a feature of 'Track Search', where the unit can seek out the gap between one track and the next, it allows track selection of music on a cassette.
•	Automatic Volume Control A useful feature that is found on high end head-units. Some have a microphone that 'listens' to the background noise and some are connected to the car's speedo. This feature prevents the music from becoming inaudible against rising background noise as you speed up.
•	Autostore The radio will 'read' the airwaves and then store the most powerful radio stations in its presets ready for easy selection.
•	Balance Control that moves the sound to the left or right speakers, to help get the best stereo effect.
•	Detachable Face Sometimes referred to as 'Removable Panel' or 'Theft Deterrent Faceplate', or some variation. This is a recent physical method for foiling thieves. The idea is that you take just the front bit with the buttons away with you. A thief cannot buy a new face for a back which he may have pinched unless he has a retail receipt for it. Kenwood makes sets with rotating faces called Mask.
•	Dolby The most common shared logo or feature between all brands is the Dolby labs' 'double D' symbol, denoting use of the tape hiss reduction system. Found on good-quality cassette machines.
•	Fader Rather like the balance control, however the fader moves the sound between the front and back speakers.
•	Full Logic This is the type of cassette deck that doesn't have chunky push-hard buttons. The mechanics of the cassette deck are electronically assisted. Good full-logic cassette decks will have power-load and eject.
•	Loudness When played quietly, we perceive bass frequencies to be less prominent. At low volumes, you hit this button and it all sounds richer and fatter.
•	MASH Multi-stage noise shaping. This is the name given to the digital advances that were introduced after the CD specification had been established.
•	Oversampling A digital electronics method for the CD machines to be absolutely certain that the information they are playing will play as music.
•	Pre-amp Output A set of chords, usually of the RCA or phono type, that extends from the back of the unit, allowing connection to an external power amplification system.
•	RDS Radio Data System. Extra information broadcast on FM along with the music that is displayed with an RDS enabled head-unit. Some will hunt down certain types of programme for you, or even traffic reports. The latter feature is only available on RDS-EON enabled head-units.

Amplifiers

•	Bridgeable This is where two amplifier channels can be combined to give one meatier version, for example, to run a big bass speaker or use a 4-channel amp as a more powerful 2-channel version.
•	Crossover Can be confusing. There are two types of crossover, active crossovers and passive crossovers. Both separate the bass frequencies from the mid and treble frequencies and send the right signals to the right speaker.
•	MOSFET A kind of amplifier power transistor (the 'engine' of the amplifier), thought to be so good that the manufacturers will generally print the fact on the outer casing of the amplifier.
•	RMS Means 'Root Mean Square', which refers to the output power of an amplifier in watts. Although it should really be qualified by stating the RMS value in relation to the music, i.e. '20 Hz to 20kHz, 4 Ohms', this is the single most reliable rule to use when comparing the wattage of amps.
•	Signal To Noise Ratio An expression to give you some idea as to how 'hi' your 'fi' really is. A reading of 90dB is a lot of signal for a little noise (hiss) and will always indicate a good piece of kit. Higher than this and your talking special. Also applies to any audio unit of any kind.

Speakers

•	Bass Reflex/Ported A bass enclosure with a hole in it. The hole is usually in the form of a piece of tubing sunk into a wooden box, and has dimensions calculated to give you the deep stuff from the back of the speaker, as well as the front, without canceling itself out - in fact, offering up to twice as much bass as without.
•	Coaxial/Triaxial/Component Coaxial refers to a design of speaker where the tweeter is mounted in front of the bigger speaker as a single item. Triaxial is a design where there are there are two smaller speakers mounted in front of the bigger speaker. Component is the situation where each speaker is a separate item. The coaxial and triaxial designs may be called 'full range'.
•	Dual Cone Method used on cheap speakers to enhance the high sounds from a single cone.
•	Midrange Speaker that handles the middle frequencies - where most vocals actually occur.
•	Tweeter Littlest speaker that deals with the high frequencies.
•	Woofer/Subwoofer Speakers for bass, from 8 inch to 32 inch in diameter.