[TrunkCom] digital and subaudible

Fri, 1 Nov 2002 09:44:23 -0600

There was actually another, and more important reason to use subaudible
data. The subaudible data on the voice channel carries the talkgroup id (or
individual radio id) for the current voice call in progress. After
receiving a call grant on the control channel, the radios switch to the
voice channel and immediately check the subaudible data to ensure they are
on the correct voice channel. This happens before the user hears any audio,
again to ensure the radio doesn't accidently pick up a wrong conversation.

What Wayne said is correct. The priority monitor just adds information on
other voice calls in progress to the subaudible data stream, but the
primary reason for the subaudible data on analog channels is to verify the
radio is on the correct voice channel.

Like Wayne, I haven't confirmed it either, but it seems ASTRO digital
systems confirm the proper voice channel by decoding part of the digital
signal on the ASTRO voice channel. This is probably more efficient and
reliable than using subaudible data, and I'm sure can be done at a faster
speed, since the ASTRO data stream is running faster than the subaudible
data stream on analog systems.

Rob

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Message: 3
From: Wayne M H <[email protected]>
To: [email protected]
Subject: Re: [TrunkCom] digital and subaudible
Date: Thu, 31 Oct 2002 20:07:32 -0800

On Thu, 31 Oct 2002 22:38:35 -0500, Brian J Cathcart
<[email protected]> wrote:

>On Wed, 30 Oct 2002 19:42:33 EST [email protected] writes:
>> I remembered searching with my=20
>> 92 last week and recieving the talkgroups for Conn SP digital trs in=20
>> subaudible.  Now if Uniden keeps the subaudible function in the new
>scanners.  That=20
>> might solve some 9600 problems.
>
>Uniden doesn't have the subaudible function.  That's a feature of the
>GRE-made scanners PRO-92 and PRO-2067.
>
>Are you getting talkgroups displayed in subaudible mode on the digital
>talkgroups, or only the analog ones?

I haven't confirmed this, I'm basing this primarily from assembling
experiences but 100% digital systems (APCO-16 or 25) do not send out
subaudible info on the voice channels. This info is sent in the
background stream of data for the voice call.

The purpose for the subaudible data was for priority monitor, which is
a scanning feature that allows a Motorola radio to switch to a voice
call and then monitor the subaudible data for a higher priority
talkgroup. So if the system can send the other active calls via the
background data stream, why use subaudible data?

-Wayne

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