Philadelphia Police & Fire both have simplex frequencies. They actually use them more than you notice, because if you are not on a fireground or in the area in which these frequencies are being used, you will not hear anything.
If you are a few blocks away, even then the signal will start getting broken up. All of the police portables are programmed with these simplex channels. You will hear something like this:
- "2BD1"
- "Proceed"
- "Can you have 214 switch to Tac-1?"
And if you are not in the area, then you aren't going to hear anything.
So the conclusion is, you'll seldom hear anyone except if Tac-Air is on. Usually you can hear the air unit from several miles away.