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Here's a good post from 1993 on making a circuit to use old phones as intercoms- Talking over the phones is easy. You put DC current through the phone and it transmits and receives audio. So two phones and a current source (about 25mA) all in series will give you a talking circuit. A suitable current source can be as simple as a 9V battery and a series resistor whose value is adjusted (with both phones offhook) till about 25mA flows. Link.
Circuit to use old phones as intercoms
Here's a good post from 1993 on making a circuit to use old phones as intercoms- Talking over the phones is easy. You put DC current through the phone and it transmits and receives audio. So two phones and a current source (about 25mA) all in series will give you a talking circuit. A suitable current source can be as simple as a 9V battery and a series resistor whose value is adjusted (with both phones offhook) till about 25mA flows. Link.
Posted by Phillip Torrone |
Aug 15, 2005 12:12 AM
Electronics, Telecommunications |
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