Telephone circuits

Telephone

Telephone amplifier, Smart Phone light, Conversation Recorder, Simple Phone Tap...


2 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.
9-Line Telephone Sharer
This circuit is able to handle nine independent telephones (using a single telephone line pair) located at nine different locations.
9-pin null modem cable
9-pin to 9-pin female
Electronics Telephone Talking Circuit
This is the basis of electronics telephone sets.
Telephone Audio Interface
Audio from a telephone line can be obtained using a transformer and capacitor to isolate the line from external equipment.
Telephone Bell circuit
This circuit was floating around on the web apparently untried and since I had recently acquired a school bell I thought I'd give it a try.
Telephone In-Use Indicator
Circuit to illuminate an LED when any phone extension is off-hook. LED should illuminate when circuit is off-hook.
Telephone In-Use Relay Controller
Circuit to close a relay when any phone extension is off-hook.
Telephone Ring Generator Using Small Power Transformer
This ring generator will ring a telephone once every 10 seconds.
Telephone Ring Generator Using Switching Supply
The telephone ring generator shown below generates the needed high voltage from a simple switching mode power supply.

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