Texas DB Confusion

[Ensnared]

I am rather confused about how patched radio systems work. In McClennan County, there are municipalities that still show active conventional licenses, but show on the HOTRRS radio system as talk groups. Does the presence of a "plug" mean that an opening in the radio system has been made for a city that uses conventional frequencies? I noticed this with the talk groups listed above the recent changes to the DB in Falls County. The talk groups in questions are listed under, "Other law enforcement talk groups." Out of these, only one has been active, 214. If anyone has caught any radio traffic on these, please let me know.

 

[rattlerbb01]

I’m sure someone can answer as to the technical side of it much more in detail than I can. From my observations, there are some talkgroups on these systems that are hard patched, for the lack of a better word, to a conventional repeater. Traffic goes both ways and they have a permanent patch unit ID when the conventional side is activated that shows up on software or your scanner. Then there are console initiated patches that show up on control channel monitoring software such as unitrunker, DSD, etc with a patch ID for the temporary talk group. These can still be heard in most scanners if you are parked on one of the original, pre-patched talkgroups as well. As for the “plug” I am not sure what you are referring to.

 

[jonwienke]

It's fairly common for specific talkgroups on a trunked system to be multicast on a legacy analog frequency. Most of those are one-way; you hear the alert tones and fire/EMS dispatch stuff on the analog frequency, but you don't hear analog static on the digital side that you would get if analog subscribers were being patched to the digital system.

Allowing analog radios to transmit on a digital system defeats the security and authentication features available on digital systems. You can jam a repeater input on a digital system, but you can't transmit false traffic without stealing an actual subscriber radio. With analog, anyone smart enough to program the correct frequency and PL tone can transmit on the system.

 

[nd5y]

There can also be talkgroups that are permanently patched to a conventional channel but do not waste trunked system resources; they don't become active on the trunked system unless one or more radios are affiliated with the talkgroup.

 

[ecps92]

One note, - not really Trunk Related, but since you mentioned it, many [in my New England experience] maintain their older systems as back-up or even Interop, when having moved to a Trunked Network, so the "Active" licenses will remain Active.

Heck, we have licenses here, for Frequencies that have not been used since around 9/11, but they renew them regularly.

I am rather confused about how patched radio systems work. In McClennan County, there are municipalities that still show active conventional licenses, but show on the HOTRRS radio system as talk groups. Does the presence of a "plug" mean that an opening in the radio system has been made for a city that uses conventional frequencies? I noticed this with the talk groups listed above the recent changes to the DB in Falls County. The talk groups in questions are listed under, "Other law enforcement talk groups." Out of these, only one has been active, 214. If anyone has caught any radio traffic on these, please let me know.

 

[Ensnared]

Thank you for the replies.

 

[rattlerbb01]

It's fairly common for specific talkgroups on a trunked system to be multicast on a legacy analog frequency. Most of those are one-way; you hear the alert tones and fire/EMS dispatch stuff on the analog frequency, but you don't hear analog static on the digital side that you would get if analog subscribers were being patched to the digital system.

Allowing analog radios to transmit on a digital system defeats the security and authentication features available on digital systems. You can jam a repeater input on a digital system, but you can't transmit false traffic without stealing an actual subscriber radio. With analog, anyone smart enough to program the correct frequency and PL tone can transmit on the system.

In the case of our local system, the Fire/EMS dispatch talk group is permanently patched to the legacy VHF repeater. If a user keys up on analog, the patched talkgroup comes up too on the P25 system. I’ve observed adjacent county fire units and air medical helos coming across that dispatch channel with the 999xxx patch unit ID many times on the P25 system talking to the dispatcher and local units who are talking on the P25 side. There are also a few surrounding counties and agencies with permanent 2 way patches between analog and the P25 system that seem to work in much the same way. I am not familiar with any of the system architecture that makes this possible as I have only been a public safety end user and scanner listener in this hobby.