Understanding Some Terminology

[LostnFound]

I've been combing the WIKI area trying to understand how a scanner actually works and have a question regarding squelch. I think I recall reading when going through RadioShack Pro-18 manual when a scanned channel is displayed there is an associated CTCSS and DCS information on that particular channel. , if my understanding is correct these are related to how squelch functions, does that mean that you have to adjust the squelch on each channel you pick up or if the CTCSS/DCS numbers are already saved it automatically adjusts squelch or am I way off?

I may need to step away from the computer,

 

[SCPD]

CTCSS/DCS are also know as Private Line/Digital Private Line. Often there are more than one user on a particular frequency, if you program the correct CTCSS or DCS info in you'll only hear the user you are interested in. For example 155.340 in NC is a statewide ambulance to hospital frequency, if I program my local hospital's CTCSS tone (167.9) then I will only hear their calls and not hospitals in surrounding counties. If no tone is programmed then all transmissions within range will be heard.

 

[Thayne]

You should just adjust your squelch so it silences the noise on a channel that does not have any signal on it and usually leave it there.
If your radio is listening in carrier squelch (open) mode it will hear all signals that are strong enough to be over the "noise floor" , including any that are using CTCSS or DCS. If you specifically set a frequency to only receive signals with certain CTCSS or DCS "tones" it will just skip over those signals as they don't match what you have programmed, and the radio may pause for a few milliseconds to analyze tthe signal but you won't hear a thing. One more thing is that if you are listening to trunked systems, the radio is just listening to control channels, so it does not work exactly the same as on conventional channels. Sorry I am so bad at explaining things but maybe this will help.

 

[Sprinter06]

Radio Squelch Tones

CTCSS and DCS or DPL tones provide privacy on a frequency that is shared by multiple users. If for example (from experience) San Gabriel CA police and Seal Beach CA police both are use 460.075. They are prob line of sight for radios 20 away from each other. They can hear other because they are so close. They each would pick a 'tone'. Then the radios would only transmit on that frequency with that tone that acts like a key. This eliminates someone else from accidentally using another's radio system.

These tones are transmitted on a frequency the human ear can not hear while the radio transmits. CTCSS is an analog and DCS is digital.

If you want to hear everyone on a channel then don't program one for that channel or on some like my HS200 it is on or off for all so you program a zero for the tone code. Then adjust the squelch knob. This knob is only used for 'open' or no tone channels you program.

If you only want to hear 1 system or user say maybe your place of work. And not someone else down the road, find that tone and enter it in. You will only hear your workplace on the channel you use. It will only break squelch and come through if it hears the right tone. Some scanners and radios have a tone search mode which is handy. Turn it on when you hear traffic and it either displays it irght away or runs thru each and then locks on to the one being used.

 

[LostnFound]

Ah so its a combination that makes it completely unique, in a simplistic way its sort of like a mac address where no 2 are the same although they share the same LAN. That's very cool , thank you all very much you all explained it very well. Basically a pyramid being drilled down.