PL stands for private line; it is a sub audio signal that becomes part of the radio transmission, from radio to radio. In the past technology used was called carrier squelch; this meant that unless another radio was transmitting on the same frequency, your radio would not break squelch, in other words, the speaker comes on.
As more and more people started using two-way radios, people started to listen to others on the same frequency. By adding PL to your frequency the radio must now be programmed for the same frequency and the same PL code. This helps reduce but not eliminate you listening to someone else’s conversation.
By no means does PL make your conversation secure; it just merely mutes the speaker so no sound comes out until both conditions are true (same frequency and same PL). DPL, digital private line works on the same concept as PL, but it’s digital. They both work pretty much alike.
Again, it’s important to remember that neither technology PL nor DPL will make your conversation secure, all one needs to do is press the monitor button on the radio to hear everyone on that frequency, regardless of PL or DPL.
Below are the PL and DPL codes used to program current radios.
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|XZ 67.Ø||WZ 69.3||XA 71.9||WA 74.4||XB 77.Ø||WB 79.7|
|YZ 82.5||YA 85.4||YB 88.5||ZZ 91.5||ZA 94.8||ZB 97.4|
|1Z 1ØØ.Ø||1A 1Ø3.5||1B 1Ø7.2||2Z 11Ø.9||2A 114.8||2B 118.8|
|3Z 123.Ø||3A 127.3||3B 131.8||4Z 136.5||4A 141.3||4B 146.2|
|5Z 151.4||5A 156.7||5B 162.2||6Z 167.9||6A 173.8||6B 179.9|
|7Z 186.2||7A 192.8||M1 2Ø3.5||8Z 2Ø6.5||M2 21Ø.7||M3 218.1|
|M4 225.7||9Z 229.1||M5 233.6||M6 241.8||M7 25Ø.3||ØZ 254.1|
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http://earlylearningalliance.org/calendar/2017-06-08/ Codes shown in red are not standard and are not recommended.