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Remote control using telephone - Here is a tele-remote circuit
which enables switching "on" and "off" of appliances through Telephone
lines. The circuit described here can be used to switch up to nine
appliances (corresponding to the digits1 through 9 of DTMF the
Telephone key-pad). The Telephone can be used to switch....(added
4/05)
Insert Text here
Room Monitor - This circuit allows audio monitoring of a remote location and so
doubles as a room monitor or baby alarm. It can be run from a 12 Volt battery or mains
power supply as shown below. Interconnect uses 3 wires, so multi core cable can be
used; alarm or telephone cable is suitable just leave any extra wires free... [Andy
Collison]
Simple Intercom - The simplest possible way to make an intercom is by connecting
two loudspeakers in series with a battery, as in the circuit shown here. One of the
speakers must be at a remote location. Sound waves impacting on either of the
loudspeakers induce a current in its coil which is translated back into sound by the
other speaker. Yes, a loudspeaker works just fine as a microphone....(electronic
design added 6/07)
The Link Telephone Intercom – Every Home Should Have One! - 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 your own home intercom between the kitchen, the garage, the rumpus room and at
your poolside ‘barby’ and all for less than $100! The “Link” intercom.... (added
10/05)
Two Line Intercom Plus a Telephone Changeover Switch - The circuit presented here
can be used for connecting two telephones in parallel and also as a 2-line intercom.
Usually a single telephone is connected to a telephone line. If another telephone is
required at some distance, a parallel line is taken for connecting the other
telephone. In this simple parallel line operation, the main problem is loss.... (added
5/02)
Use old Phones as an Intercom - ASCII format Now here's some logic that should
work fine with the right zener and the right resistors and a couple of cheap npn's
2n2222A's or 2n3904's (06's?). If you get close to 25 volts with the new smart test
boxes, a 20 volt Z may work fine. Choose R1 to limit current through Z and have enough
left to turn on npn1 just enough to deprive npn2, choose R2 for that, and you will
need to add a resistor R3 to protect the LED from overcurrent as needed, depending on
the phone system you have! (added 1/07) [richard steven walz]
