Somebody explain trunking to me please

[Jabomb9]

Okay, so I have a Pro-95 that is dual trunking. I got it programmed by rat shack (they just cloned theirs over to mine) and it works great. So I just turn it on the my county's banks (rather than the portland area banks) and look at the display when a signal comes in to determine who it is.

Problem is, I think I'm missing some of the features. I don't know what trunking is. Can somebody please elaborate?

Thanks

[erickonphoenix]

If we're listening to a known frequency and a site controller detects silence on another channel it will broadcast this new frequency through a control channel then all the listeners can move to that new frequency as needed. Your trunk scanner can pick up this broadcast and follow it just like a police radio does.

It allows for more efficient use of frequencies.

[MetalFlame]

What is trunking?
http://www.ukmidlandscanner.co.uk/trunked.htm



erickonphoenix,is that a copy/paste? :wink: 8) :wink:

[amoney]

I was about to say, trunking is hoping over to otehr frequencys, or the temporary use of a selection of frequencys for transmitting and recieving, it is an automated process as long as your scanner is programmed accordingly.

I once read an excellent short and sweet explaination, it had the perfect example demonstrating trunking, if I come across I will post back. But the above link should be sufficient.


..............

In a conventional system each agency (police, fire, DPW etc.) has their own seperate frequency or group of frequencies.

Trunked Systems are computer-driven systems with anywhere from 5 to 28 frequencies that are shared by all the county and city public safety departments. The system is designed so that each conversation hops between these frequencies.
- When a user presses his microphone key, the system automatically transmits the call on the first available frequency.
- This means that every time a user keys his microphone, he could be on a different frequency.
- The original frequency that he was using will probably now have a different agency and conversation on it.
- Because of this it is difficult to listen to trunked systems using a regular scanner.

In a trunk system:
- One of the frequencies is the data (control) channel and will have a steady buzzing sound on it
- The data channel is transmitting the data that controls how the trunk system operates.
- Instead of assigning each agency a frequency, users of the system are assigned talkgroups.
- Talkgroups are setup so that each agency will only hear their own units and not all the communications on the system.
- Each radio is programmed with a different ID that is displayed to the dispatcher and other radios using the system when it transmits.

Although it may not be psecific for ones area, it is a great crash course of info for beginers to get a grasp on things.

http://home.cfl.rr.com/scanner/scanner.htm





There was still another site that discribed the "why" the need for trunking, although it is obvious is still was a great simple explaination that also helps understanding trunking, will post if I stumble on it again...

Spectrum efficiency is the short answer, but it's not the only reason. Since channels on a trunked system are "virtual" compared to a conventional system, there can be more and flexible channels. For example, the city of Bedford has a trunked system that has 8 frequencies, but dozens, if not hundreds, of possible channels. This particular system has at least 1 channel for each of the following users: Bedford Police and Fire, Colleyville Police, Fire, and Public Works, Euless Police and Fire, and Keller Police, Fire and Public Works. That's at least 10 channels right there, and most of those users have more than one channel assigned. How is that possible with only eight frequencies? Well, it's not, at least not all at the same time, but that's how virtual channels provide spectrum efficiency. It's unlikely that all 8 frequencies will be in use at the same time. When that happens, lower priority users get a busy signal.

Well is was not the exact one, but it basicly had the same explaination... also a great intro to trunking...

http://www.bensware.com/scandfw/trunked.htm




................



This perhaps the best... too long to directly qoute, excellent information...

http://www.usascan.com/files/und-scanning.html










............

[Jabomb9]

Thanks everybody!

[Jabomb9]

ANother question - my scanner has a button that says "trunk". What is that used for? When I press it is says "ID Saved".

[tvande]

ANother question - my scanner has a button that says "trunk". What is that used for? When I press it is says "ID Savd".

You don't say what kind of scanner (that I saw anyway, sorry if I missed it) but I'm guessing a Radio Shack and that it is saving the Talk Group ID to a TG ID list so that you can scan ONLY what's on the list.

In my area, the city has (literally) hundreds of talk group IDs...most of the time I only want to hear the PD, so I have just the PD ID's in a list and I can listen to only what is on the list.

Usually you can do an ID Search which will turn up the active Talk group IDs at that time - so you know what you have to choose from and maybe start trying to decode what service (PD, Fire, Public Works etc) each TG ID is used for.

Tom

[Loiosh]

ANother question - my scanner has a button that says "trunk". What is that used for? When I press it is says "ID Saved".

You can also press and hold the Trunk button to lock the tracker onto that ID. I use this when something interesting is happening on a channel (Like PPD Events or Dispatch). Just press SCAN to return to normal scanning operation. You can program banks into your unit which will let you setup groups you ONLY want to hear.

Press the L/O button to lock out an id. Stuff like Animal 1 & 2, NCIC and Water/Traffic Signals.

You can check what banks you have programmed by pressing TRUNK, then PGM (program).