Wired local area communication system??

Hey guys,

I have a friend with a farm in an area where cell phones just do not work. He has several out buildings and would like to set up a "Local phone system" for lack of better terminology.

He has tried some wireless solutions and none have been suitable. Running wires to/from each location is not a problem and in fact at this point he would prefer to do that. He needs a "base unit" and 5-8 remote locations. The ability to go to any one of the locations and make the others ring, buzz or whatever to signal somebody to pick up at one of the other locations is needed. Doesn't necessarily need to be able to ring only a particular station (as opposed to ringing all locations) but that would be nice if it could do that.

I was thinking that there must be some sort of military surplus equipment to be able to do this but I have less than no idea what it would be. Further, once it is identified as the equipment to get... where to find it.

I know some of you specialize in military comm gear and some of you even purchase/restore/sell it. So, I'm hoping we can get some ideas here and get my buddy fixed up.

So, any ideas??
 

CARNAC

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If there is household power in each of the locations AND a means to string commo wire, he might want to try the LS147 intercom system. It can have up to 7 intercoms on the line.

If no power then I'd use cheap and easy TA312 with commo wire and replace the batteries every 90 days depending on environment and usage.
 

SCSG-G4

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If there is household power in each of the locations AND a means to string commo wire, he might want to try the LS147 intercom system. It can have up to 7 intercoms on the line.

If no power then I'd use cheap and easy TA312 with commo wire and replace the batteries every 90 days depending on environment and usage.
Or use the hand powered TA-1's for a no-battery solution. If he was just hooking up two points and A/C power was available in both places, then I would recommend a pair of the CA-67A's - pick up the handset in one place and it rings the other end. But that will not work for multiple locations.
 

sigo

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TA-1042 Digital nonsecure voice telephones will work as well. Several phones can be set up on a common power source and when you pick up one handset they all ring. No cranks or any other action required. The downside in they require four wires instead of two.
 

tim292stro

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I don't know if you know it, but the telephone is one of the simplest darn things you'll ever come across. If you're looking to do simple point-to-point comms, 3x to 8x (depending on distance) series 9-volt batteries, a resistor (OR even better, a current regulating diode), a power supply audio bypass capacitor, some twisted pair phone wire, and two off-the shelf phones - are all you need to get a comms. Outside of the wire, phones, and batteries (power supply) - that's just TWO PARTS, in total about the size of a pinky finger nail, and under a dollar in cost.

The telephone circuit is a simple loop, with current limited to 23-30miliamps (0.023 - 0.03 Amps) when both phones are off-hook. To make phones ring you need 90VAC@20Hz, this is difficult to build and potentially deadly if done wrong (same with field phones and their ring generator), but this guy came up with a neat trick to make a lower-voltage DC ringer for the other phone when one is picked up.

If you're really looking for a local phone-type intercom, look into Asterisk. This is a Linux based phone system and ecosystem (i.e. many companies make hardware of varying costs to support the total infrastructure). You can use regular 2-wire phones with a cheap adapter, and give each out-building its own extension, all wired back to a central controller. Just pick up any phone, dial the extension, and the other phone will ring (and someone can answer and talk). If you'd like you can also hook the home's phone-line into the Asterisk box and have it ring down to all of the outbuildings, or make calls out from all of the outbuildings.

If range on a farm is what you're looking for, I've found the enGenius cordless phones to be the best (cheapest I've found it today is about $580 for a base an handset) - they use 900Mhz like cell phones, so the range (with an outdoor antenna on the roof) can be a mile or two.
 
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