[Adam Ben-Dror] recently tipped us off to a project that he worked on recently. In this build he gutted an old candlestick-style phone and added modern technology to make it work as a cordless phone. We really liked this project because he married together new and old technology into an elegant package. There are a few hacks that he had to perform to get this to work. One was converting the rotary pulses into DTMF tones. The other was making the cordless phone that he gutted recognize when the phone was on or off of the hook.
Details of his build after the break.
The original single throw single pole ‘hook’ switch in the neck of the candlestick phone was replaced with a double throw double pole micro switch. This switch is used to control a small circuit that ‘presses’ the green/answer button on the doro when the earpiece is lifted and ‘presses’ the red/end button when the receiver is put down. I kept it as simple as possible using just 2 relays and 2 capacitors to create a kind of timed switch circuit.
When the receiver is lifted, 5v runs through one of the capacitors that is connected in series to the coil of one of the relays. This triggers the relay. The switch side of the relay is connected in parallel to the original answer button on the doro – the relay “presses” the green/answer button. As soon as the capacitor is charged (around 1 second) its resistance goes high and cuts power to the relay which closes again – “unpressing” the answer button. When the receiver is put down the same thing happens but with the other capacitor and relay, which are used to ‘press’ the red/end button. At the same time the other capacitor is discharged, ready to be charged again.
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The microphone and speaker from the doro were removed and the leads coming from the microphone and speaker of the candlestick phone were soldered in their place.
A small dc power socket was added to the base of the candlestick phone for charging.
A “rotatone” from oldphoneworks is installed in the base, connected to the dial and wired in parallel to the microphone on the doro. It takes the pulse signal generated by dial, converts it to a DTMF tone and sends that into the microphone to dial a number.”