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Telephone related circuit diagrams
October 14, 2010
If you feel that somebody is tampering with your telephone line you might find this little circuit useful. It detects if there is another telephone connected to the line, if there is a short or... [more]
September 27, 2010
This circuit was designed to detect when a call is incoming in a cellular phone (even when the calling tone of the device is switched-off) by means of a flashing LED. The device must be... [more]
circuit from:http://www.extremecircuits.net/2009/12/cellular-phone-calling-detector-circuit.html
September 27, 2010
If you are lucky enough to have a big house, a large garden, and small children, this project just might interest you. It’s actually a telephone ringer capable of making any mains-powered device work from... [more]
circuit from:http://www.extremecircuits.net/2010/05/telephone-ringer.html
September 26, 2010
A long time ago when telephones were so simple almost nothing could go amiss from an electrical point of view, Telecom operators installed surge protection on all telephone lines exposed to storm risks. Paradoxically, now... [more]
circuit from:http://www.extremecircuits.net/2010/05/protection-for-telephone-line.html
July 2, 2010
This is the circuit that sparked off all the other Link Telephone Intercom designs. Originally designed back in 1996 with heavy duty relays and their contact banks, it was updated late last year with the... [more]
July 2, 2010
The Link circuitry is simple and efficient, employing just two ICs, half a dozen transistors, and a handful of garden variety components. It all runs on 12 volts and is easily assembled. You can have... [more]
July 2, 2010
the Link Telephone Intercom - DTMF version [more]
July 2, 2010
This version of the Link is for those who really need a good cheap intercom that will work reliably, but without access to an outside Telco line. This could be in a pre school, a... [more]
July 2, 2010
The circuit you are about to see is the culmination of some effort at improving the basic Link intercom design. You may think that pulse dialing is 'old hat' nowadays, but the exercise of building... [more]
July 2, 2010
Although a hold feature is standard on most new phones, a lot of us still use the origional bell phones. Those of us that require a hold feature will find this circuit very useful. It... [more]
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