Huntsville, AL - Radio flaw linked to system lockup

[Thunderbolt]

HUNTSVILLE, Ala. -- Local emergency responders believe they have solved a problem that caused the countywide tornado warning siren network to fail last spring.

Radio flaw linked to system lockup - al.com

 

[jim202]

In reading between the lines here, can I guess that one of those off frequency radios hung up in the
transmit mode. Just another reason to use the "time out timer" function that all the mfgr build into the
radios, but few radio shops actually use. Another case of the tech thinking that there is no need
for a time on limit for a transmitter. It couldn't cause much of a problem.

I have made it a practice to ALWAYS set the "TOT" on the transmitters I program to the minimum
limit for the application they will be used for. In a siren response application, the on time for the
transmitter could end up being 30 seconds and still be too long for the short duration of the reply.

Radio techs working on public safety systems should rethink how they program radios.

Jim

HUNTSVILLE, Ala. -- Local emergency responders believe they have solved a problem that caused the countywide tornado warning siren network to fail last spring.

Radio flaw linked to system lockup - al.com

 

[whitstu]

I agree with you Jim. All subscriber units are 60 seconds TOT and Repeaters I have at 120 seconds TOT. Works well for what we do. I've never understood why nobody uses TOT.

I remember my dad telling me one time that a subscriber was on one of the county systems and tied up the system for an hour. The Micor repeater kept timing out of course throughout the search for the keyed radio. They ended up finding the unit which was a Standard/Vertex 110 watt mobile the PA deck was melted by the time they found it, and it was in the repair shop with the microphone shoved in-between the seats with no TOT programmed in the radio. I think the radio was putting out 1 watt or so by the time they found it. I'm not sure why the battery didn't die, must have been on a charger of some sort and this was back in the late 70's.

After that story I made it standard for all my stuff to use TOT.

 

[cifd64]

The NYPD could learn a thing or two. Listen to SOD or other command channels, every five minutes you hear CHECK FOR AN OPEN CARRIER!. I know they use TOT, but they should consider shortening the duration.

 

[radioman2001]

If I am not mistaken, FCC rules dictate a maximum of 2 minuits of carrier.On NYPD, most of the time it's a on purpose keydown. Have heard it many times, whether it was to block a specific officers transmission, or in one case I was involved was, the officer was trying to block transmission because another office was putting out info that would put officers lives at risk. They new the perp, and that he was in possession of a scanner.
BTW the TOT doesn't always work, even when enabled. Had an incident about 20 years ago, that I was called out to in the middle of the night. County PD called to say their entire radios system had failed, upon arrival I saw all voter cards showing red, meaning no voter tone. I called Telco, and kept looking for a cause since it was highly unlikely that all the phone lines coming into HQ had gone down since the telephones were still working. I proceeded up to the tower, and noticed a carrier on channel. I pulled the TOT out of the repeater so at least some communications could occur. Went back to HG and requested a roll call of all radios on that night. After about 25 min we found that a control station at one of the outlining departments was stuck on, after a vehicle pursuit in their city. Had an officer go down and unplug the station, which fixed the problem. The station was a Micor with the TOT module, which had apparently failed. That department was not happy when we sent them the bill for the emergency call out. They even tried to put the station back on line unrepaired, they where informed that it would be physically be removed if they did so.