Police Radio Sound

[Vince4798]

I always hear this sound on police radios and police scanners. It happens before someone starts talking. I've been wondering about this for years and I was finally able to get a sample of it. Can someone please tell me what this is?

https://clyp.it/ddk5qwqh

 

[ScannerSK]

MDC-1200 Signaling

Look for MDC-1200 Echo on the following page:
W2SJW - Radio Sounds

Shawn

 

[ofd8001]

That is a unique Radio Identification signal transmitted by the radio. It informs the dispatcher (and other units having decoding abilitilites) which radio is transmitting. That radio number is displayed on the dispatch console.

There is another component to that signalling, which is a distress signal. A user in a "difficult situation" can depress an orange button on the radio to send a signal to the dispatcher.