UT and open mic

[Liverdog]

Rick,

I was listening/watching using UT (beta 14) earlier this month as a unit had an open mic on a P25 system. Originally, I could 'see' the unit's ID, but then two different dispatchers (with different IDs) came on and tried to alert other units to look for the open mic on the same TG. Now, I could see the dispatcher's IDs on the same TG, but when they released their mics on the TG, and we were back to the unit with the open mic, there was no ID for the remainder of the open mic. Now, my decode rate was fluctuating so perhaps I wasn't receiving the ID back, but I always assumed that the ID of the radio was constantly being retransmitted on the cc so I should have picked it up at some point during the long open mic incident but never did. Is this just how UT processes the IDs? Catch it the first time or not at all? Just curious.

Thanks

 

[SCPD]

I always assumed that the ID of the radio was constantly being retransmitted on the cc so I should have picked it up at some point during the long open mic incident but never did. Is this just how UT processes the IDs? Catch it the first time or not at all? Just curious.

This depends - in part - on the type of system. You'll always have a radio ID on a straight Type I Motorola system. P25 issues a channel grant at the start of the call and periodic continuation messages while the call remains active. The dispatcher operating from a console (unless they're using a radio to operate from a remote location) can pre-empt the audio. Once the dispatcher drops off, the system can't tell who's radio is still keyed up on the repeater input. Eventually the radio's own TX timer should kick in to stop the transmission. Some admins may program their radios to allow very long talk times. The annoying thing is the person with the stuck radio can't hear the dispatchers' warnings while the radio is TX'ing.

I believe Motorola Type II and EDACS behave much the same.

Afterthought - I should point out that on a Motorola VHF/UHF system or a P25 system that uses "explicit" channel addressing (repeater inputs and outputs are both explicitly designated in the control channel messaging) - it is possible to re-assign the repeater input to a different frequency. This will allow re-covering the talkgroup (and everyone on it) with the loss of the one stuck-mic radio. Loose analogy: imagine a conference call where one participant refuses to shut up ("that guy has a stuck mic") ... the call manager presses a button and *poof* the talkative voice is no longer heard. Everyone else can continue their discussion.