What is PL or CTCSS / DCS
CTCSS stands for Continuous Tone Coded Squelch System (CTCSS) and is used to minimize interference to radio systems on the same frequency, otherwise called co-channel transmissions or interference. What it does is that the repeaters and radios send each other a sub-audible analog tone (you can’t hear it) that tells the radios to open its squelch to receive a signal. The sub-audible tone can be transmitted and received, to only allow radios to hear each other with matching tones.
These tones allow repeaters to not open up (read: transmit) without receiving the proper tone. Sometimes called privacy tones, these tones will allow your radio to only hear traffic on a frequency with matching tones. In all reality, there’s nothing private about them. We use them to demarcate specific repeaters across the area and allow others, who may not be members of our group, to have their systems also with minimal interference.
Sometimes, these tones are called “PL Tones”, which stands for “Private Line” and is a Motorola Trademark Name. They are the same thing.
Here is an example of a repeater listing and what it means:
GMRS Call Sign: WRME405 (This is the repeater owner registered with the Group)
Repeater Frequency Pair: 462.725 & 467.725 (462.725 would be the “output ” or frequency your repeater listens to the repeater on and 467.725 is the “input” or frequency you transmit to the repeater on. Just like the frequency list above)
CTCSS/PL Tones: 127.3 (TX and RX) (this is the CTCSS tone to access this repeater. You need to have 127.3 Hz programmed into the “TONE” or CTCSS/PL section of your radio programming.)
Each repeater in our group should use one channel each in your radio, especially if you have a radio that “identifies” a repeater by name on its readout.
DCS is a Digital Coded Squelch. Same as a CTCSS but a Digital one instead of an analog sub audible tone. You don’t hear it but it does the same thing. Some repeater owners use these and some use CTCSS. It is all personal preference of the repeater owner.