Trunked sys talkaround?

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vocoder

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Can trunked radios do talkaround mode and skip the repeater entirely using the voice channels?
Or can they do a low power talkaround mode?
2 radios on the same talkgroup talk 1 on 1

Maybe conventional mode using voice channels (without repeater) like the radios do, using 8tac channels.

I realize they can operate conventionally in fail safe mode, when controller is down.
 
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most systems have other frequency's NOT on the Trunking System for Talkaround use i'm in Cleveland Ohio and many systems have them
 

RFI-EMI-GUY

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Can trunked radios do talkaround mode and skip the repeater entirely using the voice channels?
Or can they do a low power talkaround mode?
2 radios on the same talkgroup talk 1 on 1

Maybe conventional mode using voice channels (without repeater) like the radios do, using 8tac channels.

I realize they can operate conventionally in fail safe mode, when controller is down.
I have seen radios programmed that way in the event the entire system were disabled.

I had a client that wanted back up beyond the usual redundancy and failsoft modes, so I specified three transportable repeaters to be hauled to top of parking garages, run off generator or vehicle power. Likewise the subscribers could access those same channels via repeater or talk around.

It is a contingency you don't want to use and it takes planning to test that capability as you have to disable those trunk channels from operating during the tests.

In most cases, the trunk system will run at full capacity using redundant controller equipment or will revert to fail soft mode.

I have at least once, seen a Smartnet system that failed to revert to fail soft because of a software programming error/bug that created simultaneous main/backup controller malfunctions while the "active" controller continued to send a signal to the repeater stations that kept them from going failsoft. For that customer, I designed a remote manual kill switch so that that would never again be a problem.

As I recall it was a one off problem where factory engineers installed upgraded firmware with some incorrect parameters. I say one off, but I think it happened to another customer as well. The real solution is that firmware upgrades should be done at the beginning of the week and engineers should not fly out of town without having rolling control channels over repeatedly and making sure all channels actually talk with radios. That sort of mistake gives customers the heebee jeebies., because they had no indication of being off the air at midnight until officers started calling in by phone reporting they were getting out of range tones or beeps.

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JD21960

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There are various Admin channels or traffic talk-groups. But like he said, most use other channels for local talk-around. Our Police have been Enc for years. But the old city talk-around is analog, still in heavy use and they rehash everything they do on it after a call. I always leave all the old analog system Conventional channels for my area in my scanlists. Our Country Sheriff uses their old main channel as a talk-around a LOT at night.
 

RFI-EMI-GUY

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most systems have other frequency's NOT on the Trunking System for Talkaround use i'm in Cleveland Ohio and many systems have them
Before 700 MHz, was allocated here in Florida, We were lucky enough to get trunk channels in the Miami Dade Metro area. I had to constantly explain to clients that a channel that was clear in City of North Miami, could not be used anywhere else in the huge county. Folks sort of saw some "portabilty" in the channels which does not exist, you can't take them from one city and move them just 10 miles south because, then you are 10 miles closer to Monroe County and they own the channel.

So most radios operated within the confines of the trunking fleet plan or on the NPSPAC mutual aid channels.

What the cities and counties in southeast florida did not use, the State of florida took hold of.

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INDY72

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Yes you can do conventional talkaround in both p25 and analog modes in addition to the trunking. Hence all the 8tacs 7tacs etc. And with the newest radios you can do it on multiple bands.

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ofd8001

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Our local system does that and I'm familiar with another. They are typically simplex channels and the frequencies are separate from those used on the trunked system.

These simplex/talkaround channels are critical because there are areas that are out of range of the trunked system. For example firefighters could be going into a sub-basement. Of course they'll have to let the incident commander know there is a need to use the simplex channels.

The way our radios are programmed is that System 1 is the trunked system and System 2 is the simplex channels. I think those national interoperability frequencies may be System 3.

From a user standpoint, all that is needed is changing the channel selector to the simplex channel and the radio does the rest.
 

slicerwizard

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most systems have other frequency's NOT on the Trunking System for Talkaround use

Our local system does that and I'm familiar with another. They are typically simplex channels and the frequencies are separate from those used on the trunked system.
The systems don't have or do anything. The simplex channels are not part of a trunking system. They're an independent alternative/backup.
 

INDY72

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We have one freq that IS part of the trs here that IS also the designated talkaround repeater for the system. Has been even back in the analog days before P25 conversion.

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troymail

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Can trunked radios do talkaround mode and skip the repeater entirely using the voice channels?
Or can they do a low power talkaround mode?
2 radios on the same talkgroup talk 1 on 1

Maybe conventional mode using voice channels (without repeater) like the radios do, using 8tac channels.

I realize they can operate conventionally in fail safe mode, when controller is down.

As others have said - there are various ways for doing these types of things.

Some "talk-arounds" are simply a different talkgroup on the system but still using the repeater (mostly for greater distance I would assume).

However, as you suggest, some systems (not really on the system) - many very old - even have conventional frequencies for low power direct communications (typically analog). These bypass the repeaters in part because that may actually be why it is being used - the users cannot reach the repeater. Situations for us may include: interior building communication, units are out of their normal locations (another state or county), and/or they just don't want anyone to hear them talking (at least not normal users on the system).

In some cases, it would seem they discourage use of these channels because they are in completely different programmed radio "zones" which take more time and effort to switch to. Still, in other cases, for safety reasons, these "direct" channels are easily accessed within the same primary radio user zones - and it's just a turn of the channel knob.

Frequency usage for these non-repeater talk-arounds vary from location to location. Some jurisdictions have licensed their own frequencies while others use common VTACs, 8TACs, etc.

As far as 1 to 1 -- that sounds like what is called "private call". These typically go through the repeater but are direct radio to radio calls - almost like a phone call vs. a broadcast on a talkgroup where all users on that group can listen.
 

Project25_MASTR

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Too many different ways to do things, not a true standardization of defining channel names.

Example, the trunk system I maintain a typical hierarchy of channels would be Primary Dispatch>Regional Operations>Inidvidual Tactical Channels (which can be on or off system depending on the situation but usually always passed through some sort of infastructure)>Talk Around (true simplex, off system). Then there's Regional and System Wide interop talkgroups...instead of limiting affiliation to a specific county you have multi-county up to system wide talk groups.

Of course, you may not see this kind structure in smaller systems.

Failsoft is a last ditch effort to keep the system running. I've only seen it once so far (it was caused by a technician doing PM work who wasn't thinking clearly and disconnected both controllers from the switches at the site) but usually what I run into is site-trunking more than anything else. Switch failures are more important than router failures as you actually will loose capacity with a switch failure versus going into site-trunking with a router/link failure.
 

vocoder

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We have one freq that IS part of the trs here that IS also the designated talkaround repeater for the system. Has been even back in the analog days before P25 conversion.

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Is the sole talkaroung freq united with a discrete repeater?
Is this part of SAFE T?
 

ofd8001

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Is the sole talkaroung freq united with a discrete repeater?
Is this part of SAFE T?

The notion of "talkaround" means that you are "talking around" or bypassing the repeater. This term is more or les synonymous with simplex (radio to radio versus radio to repeater to radio).

This happens when a user is unable to talk into the repeater because of many reasons: too far away, in a dead spot (95% coverage area means 5% dead spots) or the nature of your communicates is such that you don't want them heard a long distance away.

There is another concept, that being "Direct". For example a radio transmits on frequency A which is the repeater's receive frequency. The repeater "repeats" the transmission on frequency B, which is the radio's receive frequency. When "Direct" is chosen, the radio switches to another channel, that being frequency B (repeater output). Users are talking to one another, but remove the repeater from the communications link.

Some systems may be set up so that their talkgroup channel is one of the voice channel frequencies, or they may use an entirely different frequency for simplex/talkaround purposes.

If you look at the Jefferson County Metro Safe system, https://www.radioreference.com/apps/db/?ctid=1044 you'll see there is a simplex frequency 856.2625, but the "regular" trunked system has 22 other/different frequencies that are control channel or voice channel frequencies.

As noted above, there could be several methods, all depending on the creativity of the system designer.
 

INDY72

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IDPS S1. It is the output freq. Not input.

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