Controlling multiple base stations over single leased line?

[adlertom]

I'm looking to tone control three (3) base stations at a remote location. The specific hardware would include a Zetron 4010 console at the dispatch location, and a Micor single channel base, a MSR2000 4 channel base, and an XTL5000 "consolette" 8 channel base at the remote location.

The obvious solution is three separate leased telephone lines, one for each base. I was wondering however if there is a cheaper solution, perhaps some way to multiplex the tone control of all of them onto a single leased line, or at least something less than a T1.

Thanks in advance for any ideas/suggestions.

Tom

[d119]

Sure you can do this. Simply assign keying tones to radios and don't include one radio's keying tones in the other radio.

IE.

2175Hz = Guard Tone

1950Hz = Key F1, Radio 1
1850Hz = Key F2, Radio 1
1750Hz = Key F1, Radio 2
1650Hz = Key F2, Radio 2

etc.

Simply don't allow 1950Hz to do anything on the base stations you don't want to key.

The downside to all this is as follows:

This will be a real PITA to do on the MICOR, so you might assign it's tones first based on what's already in it.

The return audio coming from the base stations back to the console will all be mixed, and there won't be any way to mute the base stations unless you program in bogus channels into the radios and assign Radio #1's key tone to select the bogus, no-tx channel on radio 2.

If this is a Public Safety operation, you're well advised to go single wireline to each base station. You could also order a T-carrier circuit, and put channel banks on each end to break out the individual circuits for each base station, and then you're only paying for 1 circuit with 24 time slots on it (24 DS0's = 24 "4-wire" leased lines). This is probably going to be much more expensive than just 3 leased 4-wire or 2-wire duplex circuits.

[Bill_G]

That's exactly what I do on one system with 12 channels at 6 sites. But, I have the luxury of a 28T microwave tying all the sites together. It kept me from having to route xmit control through aux i/o cards in the CEB. I considered telling him about the plan, but didn't have a way to mux the rx on an analog line. I wasn't going to recommend using DSL & NXU's either since (a) tone control farbles so easily through ip connections, and (b) the asymmetry of DSL might not let him return (upload) three receiving channels at once depending on the quality of the remote site connection. I too think he is going to have to use leased lines, or find a way to build a link to the site - preferably a T1, not an IP. His final option is building three rf links if he can get the licenses and has the path.

[d119]

We are using Motorola PTP series microwave in 4.9GHz to backhaul ethernet to one site. At each end of the link is a RAD IPMux that uses CESoPSN to place 16 T-1 circuits on the ethernet. Works pretty well, and it's a lot cheaper than Harris microwave.

[Bill_G]

What kind of latency are you experiencing? Last time I measured an ipMUX, it was over 23000us, and I had to add significant delay to the rcvrs returning through telco and MNI CM11 to get the audio to line up. OTOH, the delay was stable and the link was good enough to carry tone control without dropping out (as opposed to DSL where delay and link quality are constantly changing).

[d119]

The system is part of a SmartZone simulcast and uses TeNSr channel banks, so delay is automagically calculated and accounted for.

[Bill_G]

Ah yes, the dsm card. vurks goot.

[adlertom]

Thanks for the replies. This is a backup site for a police department. Should the main site suffer a catastrophe (lightning strike, windstorm blows down tower, etc) we would switch to and use the base stations at this 2nd site.

Because of this, I don't want to use microwave or RF links, as those would have to go on the tower and defeat the above purpose.

One of the base stations at the 2nd site is our primary public works base, so I need to keep the audio paths for each of the three base stations separate. Having them all mixed wouldn't be acceptable.

We currently use leased lines for our voting RX sites and those have proven reliable. For this application (needing three paths, all to/from the same place) I was wondering/hoping that there might be another option. If not, we'll just bite the telco bulllet and purchase 3 leased lines.

I should also add that this whole situation is somewhat temporary, as we're expecting a new countywide TRS to come online in a few years. There is also the possibility of city owned connectivity between the two locations someday. These serve as other arguments against a microwave link, or anything else that requires a large expenditure up front, even if it would save $$$ in a long run scenario.

[Bill_G]

Well, if you can live without tone control and can convert to E&M keying, then a dsl / nxu solution might be the cost cutting solution you need. A single dsl is a lot cheaper than three leased lines. Add up the costs for six NXU's (approx $600 ea though YMMV), a vpn tunnel appliance like DCB, and your labor, against two to three years cost of leased lines to see if the roi pencils out. The nice thing about a dsl connection is it can be accessed from anywhere. If your dispatch center has to be abandoned, you can create a new one on the fly from anyplace with connectivity.