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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 __ Designed by Andy Collison
Simple Circuit 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 __ Designed by Hans Summers
Simple Circuit Intercom - use a telephone as an intercom __ Designed by © 2008 Ayman CDMA
Simple Intercom Circuit - The circuit of a two-position intercom is presented here. This circuit is very simple yet it functions quite satisfactorily. The circuit does not involve any complicated switching. The switches S1/S2 must __ Electronics Projects for You
The Link 4+0-Internal Intercom - This version of the Link provides four internal intercom phones with no outside line access. __ Contact: IQ Technologies
The Link Telephone Intercom - 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 __ Contact: IQ Technologies
Transistorised intercom - Several intercom circuits have appeared in EFY using integrated circuits. The circuit described here uses three easily available transistors only. Even a beginner can easily assemble it on a piece of __ Electronics Projects for You
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
Two-Line Intercom cum Telephone Line Changeover - The circuit presented here can be used for connecting two tele phones in parallel and also as a 2-line intercom. Usually a single telephone is connected to a telephone line. If another __ Designed by © EFY Enterprises Pvt. Ltd.
Two-Wire Intercom - This Intercom is powered by two 9-volt batteries and uses only current when the Intercom is used. Both units are connected via a two-wire little cable or simply two wires. __ Designed by Jan Hamer
Use Old Telephones as Intercom - You may wish to use a 12 to 24V battery, like a Gel Cell, since the car power or cheap power wall wart style supply is probably too noisy. You may have to adjust the resistor value (1.2K for 24V). Whatever gets the phones working and does not use more than 30mA total loop current. If you can manage it, get two speakerphone-type phones. Leave them in "speakerphone" mode continuously and pound on the keypad to attract the attention of the other end. __ Designed by Tomi Engdahl
Use Old Telephones as Intercom - 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. You can then bypass the battery and the resistor with a capacitor to couple the audio straight across and get a loud and clear connection __ Designed by Markus Wandel |
