Batboard

Bear with me while I try to explain the messed up setup we have and maybe everyone will be able to give suggestions on where to go from here.

We have a state wide systems consisting of repeaters in every county. Each repeater is same freq different pl. If I understand this right a mobile unit transmits to the repeater which transmits to our local repeater and we hear the receive side of the repeater, which goes by T1 to our Comtegra console.

Where the repeaters are too far from our repeater we have a T1 line to a repeater in the area with the same type of setup.

Each T1 line has the repeater and a local base transmitting on simplex for a back channel so to say.

The problem with the comtegra is we can only support 2 T1s. One on each side of the Comtegra.

We are looking to add more T1 lines to accomodate other parts of the state. This would require going to a different console. We would like to switch to a touch screen or computer based console.

The question is:

1. Would we be able to put some type of pl encode/decode at each T1 site to enable us to tell in dispatch what tower is keying up?

2. What would be the best place to look for something like this?

3. Would it require any hardware besides the console w/ the T1 line already in place?

I know it's not much to go on. I don't know if they have a CEB at the base/repeater site or what, I am scheduled to go over there next week.

I am trying to get some suggestions together for the communications committee. I though about enabling MDC on the mobiles, but they have syntors so that is out.

We are trying to get some more officer safety out there. The way it is now, if an officer keys up and we don't catch the squelch tail, we don't have any idea what tower he is on.

What we would like to do is similiar to the Centracom Gold for example. How it has the blocks on the screen for channels, we would label one county 1, next, county 2 etc.

This way we would see a recieve icon on a block and know the officer keyed up on the county 2 channel. Does that make any sense?

Questions? I'll do my best to answer.

Thanks for any suggestions.

"...We have a state wide systems consisting of repeaters in every county..."
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You have 254 repeaters connected to a Comtegra console? 254 different PL codes to select them?

It isn't clear from your description just how the backbone works - but it sounds like the repeaters share a common path [sort of like a party line].

The ideal thing would be to have a dedicated circuit from each County's repeater come back independently to the dispatch point - BUT - you may have a hard time finding a console that can display 254 channel resources simultaneously.

Well we don't have that many. We have 2 dispatch stations so the state is divided in half. And some of the smaller counties share a repeater with the county next to them.

We actually control and dispatch for 97 counties with about 50-60 repeaters.

Forgot to add, we are using the same channel for half of the counties we cover.

Example, we select one F1 on one side of the console, push page, dial a three digit dtmf and wait for the squelch to break on the repeater we are calling.

I don't know what a party line is, but it might be.

I am trying to get them to just hire someone to evaluate what we need, but my supervisor says "Oh, he's into radio stuff, so he would know"

Yeah, right.

I would love to have a circuit to each repeater. That would be simple and un complicated, but our state agency doesn't care to spend any money on law enforcement much less radios.

There idea is "There's nothing wrong with what we have, I can still talk to such and such from mine."

"...I don't know what a party line is..."
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In the olden days the telephone company didn't have a line to each customer [particularly in rural areas] so several customers had phones on the same pair. Incoming calls were distinguished by different rings - later different ringing frequencies were used so only one customer phone would ring.

I'm sure several folks will be thinking up suggestions for you - meantime you might look at Zetron's wide area system:

http://www.zetron.com/pages/english/products/racs.html

I had another thought for you. Your actual question was: "Would we be able to put some type of pl encode/decode at each T1 site to enable us to tell in dispatch what tower is keying up? "

Here is one possibility. Use MDC signalling. There are several companies that market MDC encoder boards. Usually these are installed in a mobile radio to ID the unit to dispatch.

In your case I would put one of them at each repeater. Instead of being connected to the transmitter, it would be connected to the receiver. The receiver activity indication [COR] would connect to the ID board PTT input. The ID audio would go down the receive line to the console. Since the path is wireline, not RF, you wouldn't need any pretime. Thus the overhead for the MDC packet would only be 173 ms.

You would program each repeater ID board with an MDC number corresponding to the County where it is located. [Anderson = 0001, Andrews = 0002, Angelina = 0003, etc.] At the console end these numbers would alias back to the County name. You might be able to do that with the Comtegra or you could add an aftermarket PTT ID display device.

This way, every time a user transmits to one of the repeaters you will get the location at dispatch.

You have a process for selecting a repeater from dispatch. Depending on exactly how that works, the particular selected repeater could be configured to not send the MDC ID for user transmissions it receives while it is selected. In other words - the only time you would get an ID display is when someone is trying to get hold of dispatch.

The whole thing could be pretty cheap - maybe $100 per repeater for the parts - and would not require you to change your current connectivity [although you might want to do that over time to evolve your system to greater capability]

That's a good idea.

The whole problem is money. They are willing to spend the money on the console to get in the counties that are not covered by a dispatch but not to upgrade the entire system (which is what we desperately need).

The main thing we would like to be able to accomplish at this time is tower identification. As we update the mobiles, we could get unit identification.

The best way I can figure until I go to the main repeater/base site is using dtmf through the T1 to the main site you "dial up" the tower. I have been told this changes the pl going out and gets you the appropriate tower.

The main problem with this is when you lose the squelch on the tower, you have to dial it again.

Hopefully, when we are done we will at least have an upgraded dispatch and the availability to select automatically a tower and to be able to tell which tower the unit is calling from. Hopefully we will also be able to slowly upgrade from there.