Radio Preceding Tone

[Ernest1001]

Can somebody tell me about the preceding tone I hear on the Motorola Radios used by Nashua Fire? I understand that when a user presses the PTT button a 3 beep tone it emitted by THEIR radio as part of the trunked system letting the user know that the system has recognized the radio, processed the request to transmit and that it is okay for the user to talk. However, what is the single tone sounded out of the OTHER radios preceding the communication when one radio keys up the microphone. I notice this sound is only heard on the fire department radios and not by any of the other radios in the system, such as those used by police. I think it is a useful feature of the radios as it lets the firefighters know to begin listening to a transmission, but I am not sure if this has to do with it being a trunked system or if it is a feature of the Motorola Radios they are using.

[RKG]

Without hearing exactly what prompts your question, I'm only guessing, but two possibilities come to mind.

If the FD radios are scanning, and if the transmission that causes their subscribers to beep comes in on the priority channel with the priority beep turned on, that could be what you're hearing.

Many Fire Departments have conventions for alert tones to be sent by the Fire Alarm dispatcher prior to sending certain classes of verbal message. In most parts of eastern Massachusetts:

A steady 1KHz tone is a general alert, usually preceding an information message (e.g., street closings, channels in or out of service, or the like).
An intermittent 1 KHz tone means that a message will be sent that is addressed to a company whose status is "On the Air" (as opposed to "In Quarters").
A warble tone means an urgent message follows, such as an order to evacuate a fire building.

[Ernest1001]

The sound can be heard on this video at 1:26

YouTube - Overview of new Radio Changes

It is the same sound that is emitted from the radio when a button is pressed on the radio.

It can also be heard throughout this video, a good example at 5:50. This is actually a video of Nashua Fire on the scene of a fire and you should be able to clearly hear what I am talking about.

http://www.youtube.com/watch?v=jlrBBofLZ6Y

Although I am open to any ideas because I want to learn about this sound and why the radios emit it before a transmission is received, I don't get the feeling that your idea is what this tone is really for.

[jmarcel66]

It sounds like the scan priority tone common on most Motorola portables when the unit is in scan and has a priority channel set. It's usually the channel the radio is on or "Selected".

Traffic on other channels will simply be heard. But if the the selected/priority channel has traffic, it'll beep indicating the traffic is on the channel the user is operating on.

I happen to know the Pump Operator in the video and I'd imagine the scan was on his radio.

[Ernest1001]

Thank you both. I just was curious about it and wanted to find out what it was for. Since you both said the same thing I am inclined to believe that is probably a scan priority alert.