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I'm looking to build a small telephone network with up to 10 phones to be basically an intercom system. I need any phone to be able to call any phone. I need help with a switchboard of some sorts.<p>I plan on using some inexpensive phones I found at Walmart for around $8.<p>Anyone out there know where I can learn more about telephone switching systems or can give me a jump start of some kind ??<p>thanks in advance <p>[ September 03, 2003: Message edited by: Jeremy ]</p>
One starting point would be a web site about the telephone system (www.telephonetribute.com). This has some technical information and links to other sites. The point of view is historical, but the basic telephone instruments have used the same interface for about seventy years.
The telephone system operates on 48 VDC (nominal). Phones that don't plug into an AC socket use this for power as well as signal line. When the handset is taken "off hook" the unit draws current from the line which alerts the switchboard. For a simple 10 phone system, you could use just one tone (0 thru 9) to route the signal to another phone. Once the line is selected, the switchboard can ring the other phone and when it goes off-hook, stop the ringing so a conversation can start.<p>This is not going to be a simple or cheap system!
It's possible the "cheapest" homemade system might not be homemade at all. As small businesses upgrade their switching systems, they scrap out their old phone systems. Might want to look there -- you could get something for a song that could allow you to have intercom capability and a lot of other features. Many times, you can get these, with the manuals and all the old phones, for a properly placed case of libation and a sawbuck or two, as long as you promise to chuck what you don't need in someone else's dumpster. I know a phone tech who has done this with an 80's vintage system (he used to repair/upgrade them) in his own house, and he likes the results.<p>There's nothing like getting your hands on some real equipment to learn about telephone stuff.
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for a simple "intercom" only system, you can get an intercom system and power supply by watching ebay or asking an old telephone guy.. we used them in 1A2 systems for years.. that was the old key system that you found almost every filling station, bank, realtor, store, etc.. had phones with a 25pair cable going into them.. the little intercom system was an electronic add on that usually measures about 5 or 6" tall, 4 or 5" wide, and about 1 to 2" thick.. depending on how many stations it was for.. the 10 station is relatively small... these units used the key system power supply to give talk battery, signal (usually 10vac for buzzers, but could be ring voltage for a ringer if you wanted).. plus their operating voltages.. they have a 25 pair amphenol ended cable that plugs in and punches down on a (usually) 66M1-50 block for cross-connecting.. as a stand alone, you would just connect the T&R and signal lead to each phone assigned to that station... they have exceptional quality talk and signalling and last forever.. just pick up a phone and dial the station number, it sends a burst of signal each time you dial that station.. I used to have a couple 2 or 3 laying around, will check my stockade to see what dwells in the black hole.. otherwise, just ask around, someone somewhere has a little blue box like the above.. they were cheap then, there either free or cheaper now..
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