Is encryption being used here?

[derota]

I was recently within close proximity of a police officer that was responding to a residential gas leak. (I know that my county uses a p25 trunked system). He was talking to someone on his portable and it took about one second from the time that he pressed the button to hear an electronic sound that sounded like a lower pitched Nextel chirp. It was then after this "chirp" he could talk. Is encryption being used here?

[bezking]

The Chirp is called a Talk Permit Tone, and the only thing that tells us is that he was on a Trunked system. It doesn't tell us whether he was using encryption or not. The only way for a radio user (not scanner) to see if he is using encryption is to look at the radio's display or check the position of a button or switch. What the chirp technically means is that his radio, after sending a Request to Talk signal, has been issued a channel grant (been assigned a frequency to use) and he can now start talking.

[radioman2001]

The three beeps obviously are the permit tone for the trunking meaning go heard and talk. If there were a next tone a single beep can be either a MDC ID or a Clear alert tone. If the officer was using encryption and had it turned off that beep warns him of that fact. If the officer was in encrypted mode there should be no additional beep.

[bezking]

However, that beep (called the "clear alert tone") can be disabled as part of the programming, so it's not necessarily going to be there.

[radioman2001]

True it's not hard and fast rule , but I have yet to have an agency that disables it, with the exception of undercover units that don't have permit tones either.

[derota]

Thank you.