Volume: This controls the output volume of the speaker inside the CB. It would also control the volume of a speaker plugged into the back of the CB.
Squelch: When there is nobody transmitting on a channel all you hear is noise, to get rid of this noise you increase the squelch until it has cut off. However, you will still receive all other stations. If you turn up the squelch even more, distant stations will also be cut out, if you turn it up to maximum only very strong or local stations will be heard.
RF gain: This is similiar to squelch but it does not cut out the noise. The RF gain attenuates incoming signal. It only reduces the signal strength of which you are receiving them at, so very strong station will be slightly affected while distant stations will not be heard. This does not actually affect their output signal, it only affects the signal you receive.
Mic Gain: This controls the output loudness of your voice that other stations will hear. This is normally left at maximum, the more you reduce it the quieter you will be. It does not effect the carrier wave of the radio, only your speech. If you turn it to minimum you will not be heard, but your radio will still transmit and empty signal. On AM only your carrier wave will exist, on SSB however, there wont really be any evidence that you are transmitting at all.
ANL & NB: The ANL stands for Automatic Noise Limiter and that's exactly what it does. Your voice will be carried over the airwaves by a carrier wave if using AM/FM or similiar. However, in heavily populated areas a lot of noise is generated into the airwaves. This noise comes from power lines, machines, computers, cars & the earths atmosphere. Therefore, when trying to sift through noise and intelligeble signals the noise can be too strong. Therefore, the ANL will aid in reducing this noise to clarify incoming voice signals. It will filter out the audio frequencies that the noise can be heard at and leave the frequency area of voice communication open for use.
PA/CB: This switch simply switches the CB off when switched to PA and diverts all audio output to a loudspeaker plugged into the CB instead of transmitting it via airwaves. PA = Public Address. When it is switched to CB the radio will operate as per usual.
Clarifier or 'delta tune': This variable control alters the actual frequency of which you are receiving. This is only used on SSB mode. It will generally let you go 2.5kHz below or above the actual channel you are operating on. On SSB, the transmitted signals may drift slightly and the person you are receiving might not be exactly on 27.305MHz, but actually on 27.3049MHz. This is a fairly significant drift off the desired frequency, so you turn the clarifier until their voice is clear. Otherwise, their voice will either be high pitched and squeky, or deep/muffled.
CH9 or CH19 switch: This switch only makes the radio switch to channel 9 (Australia) or 19 (America) to quickly access the emergency channel/road channel.
Duplex: This button exists on UHF CB systems which simply puts the radio into the mode where it transmits on 20 channels higher than what it is receiving so you can speak through a repeater. (Repeater information in the UHF CB booklet section)
Selcall: This stands for Selective Calling. You can use this function to selectively call a friend over the air. More information contained at http://www.roity.com/rc/selcall.html
The signal meter on a CB might be made of little lights, or a moving needle. In any case, it's only a relative representation of the incoming signal generally on a scale from 1 to 30+. It does not directly represent station distances, it only gives a differentiation of who's coming through better and perhaps just how close they are.
A sport called 'fox-hunting' exists on Amateur radio when a group of different tems of operators gather together and hunt down a hidden transmitter. This usually requires the use of cars and specialized modern equipment. Signal meter type equipment becomes very crucial in this sport. It's not just a theoretical or radio based sport though, it becomes physical when having to rotate roof mounted car aerials and handle the car, plus the on foor running with handhelf radio equipment.
Tone: This is a method used on commercial operated radios and
CB's (UHF) where the radio transmitting must generate an underlying tone
to your voice so it will actually receive it. If you don't have the desried
tone, you wont be heard by the receiving radio. This is again done using
Integrated Circuits inside the radio. This is only used on some radios,
not many. It has to be done between 2 or more people to be of any use,
and they have to share the same tone frequency. It's usually a very low
frequency hum, that can be physically heard. If you put in a breaker on
a channel where everyone is using tone, you will not be heard. If tone
is not used, the radio is generally termed to be in 'open' mode. The tone
method is called CTCSS. In Australia
the use of CTCSS is not legal on CB.