Telephone off-hook indicator
Description. The circuit depicted here can be used as an indicator when the telephone receiver is off-hook. The circuit can be in corporated with old telephones that does not have such an indicator....
View ArticleFM telephone bug.
Description. A simple telephone transmitter circuit that is ideal for transmitting the telephone conversation through small distances.The circuit is very simple and uses only few components.The entire...
View ArticleRinging phone light flasher.
Description. This circuit can be used to glow a bulb or turn a alarm when the phone rings.Using this circuit nuissence of telephone ring at night can be avoided. When the telephone rings the line...
View ArticleContactless telephone ringer circuit
Description. The contact less telephone ringer circuit can produce a ring as well as a visual indication when a call comes.The main advantage is that since there is no direct contact between the phone...
View ArticleTelephone pickup preampliifer
Description. Here is a simple circuit based on IC uA 741 that can be used to pickup voice from telephone lines without even contacting the line. If a high impedance magnetic core is placed near a...
View ArticleTransistor intercom circuit.
Description. Here is a simple but effective intercom circuit that is based fully on transistors.The circuit is based on a three stage RC coupled amplifier. When the pushbutton S2 is pressed, the...
View ArticleTelephone transmitter
Description. This is a simple, but very useful circuit that can be used to transmit telephone conversations. When the telephone receiver is on hook the voltage across the lines will be about 48 volts....
View ArticleTelephone in use indicator.
Description. Here is a simple circuit that can be used as a telephone status indicator. When the telephone is in use (off hook) the transistor Q1 switches ON making the red LED D2 glow. When the...
View ArticleTelephone operated remote
Description. The circuit given below is of a telephone operated DTMF remote. The circuit can be used to switch up to 9 devices using the keys 0 to 9 of the telephone. Digit 0 is used to switch the...
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