CTCSS/DCS

[qjschum]

I am new to scanning only ben at it for about 2 months, can you explain what this does?

[gmclam]

It is a sub-audible tone transmitted in addition to the voice. Typically, one will program their receiver to ONLY open the squelch if the tone is present. One purpose; two "groups"/etc can use the same frequency and you'll only hear audio when it is your group talking (of course both still can not transmit at the same time).

DCS is a digital form of the same thing. Scanner hobbyists will program in tones to help ID who they are receiving. You might have 154.190 with CT of 162.2 and a second entry of 154.190 with a CT of 118.8. Each has its own unique text description. When you receive a signal, the scanner displays the correct description of you you're receiving.

More info in the Wiki or here

[dmg1969]

I just bought a BC125AT and it is the first scanner I have owned that can do this. Think of it this way. The county you live in uses a certain frequency for their fire dispatch (I will use mine as an example...46.20 MHz). Now say that a neighboring county uses that same frequency for THEIR fire dispatch (or for something else like their fire ground channel or fire police), but you don't care to listen to them. If your county uses a tone, you can program that in and you will ONLY hear your county's fire dispatch...not the neighboring county. Hope that helps.

Dave

[jaspence]

Under low signal conditions, it can prevent you from hearing a transmission. Many two way radios have a button to temporarily disable CTCSS/DCS for this situation.

[gmclam]

Originally Posted by jaspence

Under low signal conditions, it can prevent you from hearing a transmission. Many two way radios have a button to temporarily disable CTCSS/DCS for this situation.

And it is real useful when monitoring a noisy signal such as on low band VHF as the squelch only opens when there is a decent enough signal that you want to hear it.