[TrunkCom] EDACS System Questions

[Scott R. Havens]

My answers are as follows:

1.  The EDACS "buzz" occurs on ALL radios, AFAIK (even those used by
professional clients of the system).  It might be less frequent on their
radios due to tighter specs, etc., but it's been known to show up on their
radios as well.  To the best of my knowledge, the "buzz" really doesn't do
anything in terms of system operation.  When EDACS was first introduced, it
was sold as a "scanner buster" system.  The logic was that evil snoopers
like you and me would not be able to tolerate the rude noises the system
makes when monitored through a conventional scanner, and therefore we would
not try to eavesdrop.  Now that EDACS scanners are commonplace, all of the
anti-scanner "window dressing" is pretty much an anachronism.
Unfortunately, nobody at Ericsson has thought it worthwhile to get rid of
it.  After all, there might be 5 or 6 "scanner heads" out there still trying
to listen to it with non-trunking receivers!

2.  I'm not sure what's causing your "white space" problem.  If you're not
hearing the beeps at the end of the transmission, I would suspect you might
have entered the frequencies in the wrong order (although I'd expect the
radio to just be silent and squelched during the missing replies, rather
than giving you a dead carrier).  Or you may have set the radio to use
carrier squelch only, rather than responding to the commands from the
control channel (if that's even possible on an EDACS system!).  In my own
experience, I sometimes see a similar effect when the signals get very
weak... but I always hear the beeps when that happens.

3.  I-Calls are transmitted just like any of the TGs you're interested in,
but you might think of them as dynamically assigned talk groups that only
include the two stations that want to talk to each other.  If you take the
radio out of trunked mode, you MIGHT hear the exchanges between the two
stations, but you'll also have to contend with all the buzzes, beeps, and
other garbage that characterizes the EDACS "landscape."  With a BC-780, you
can listen to I-Calls in trunked mode, and it sounds like the two officers
are just talking to each other on the phone, or on a private radio channel.
Unfortunately, the Pro-94 does not have I-Call capability.

I hope this helps clarify things for you.

SRH/AB2V
Tampa Bay, FL
(In the Land of EDACS, where the Shadows lie!)

> > My questions are these:
> >
> > 1. Every once-and-awhile, you will hear a few seconds of the data
> > channel come across on one of the voice channels and then disappears.
> > ... It seems this is
> > some type of data being transmitted as none of the units in the patrol
> > cars nor the handhelds are picking it up. Any ideas?
> >
> > 2. Some of the traffic is followed by a period of white space. You can
> > hear the end of the transmission, but the carrier stays open for a few
> > seconds longer...
> >
> > 3. Finally, does anyone have any idea about where I-Call's are
> > transmitted? ... I am scanning with a Radio Shack Pro-94.
>