Telephone In-Use Relay Controller
Telephone In-Use Relay Controller circuit diagram
Telephone Audio Interface
Audio from a telephone line can be obtained using a transformer and capacitor to isolate the line from external equipment. A non-polarized capacitor is placed in series with the transformer line connection to prevent DC current from flowing in the transformer winding which may prevent the line from returning to the on-hook state.
8 Line Intercommunication using 89c51
This project is aimed to make the low cost intercom system by which eight telephone lines can be interfaced with this hardware.
Telephone Hold Button
Although a hold feature is standard on most new phones, a lot of us still use the origional bell phones. Those of us that require a hold feature will find this circuit very useful.
Ringing Phone Light Flasher
This circuit is extremely simple, therefore there is less chance of any problems. It can be placed anywhere on the phone line and it will record any conversation on any phone on that line.
Phone Busy Indicator
Have you ever been using the modem or fax and someone else picks up the phone, breaking the connection? Well, this simple circuit should put an end to that. It signals that the phone is in use by lighting a red LED.
Cut Phone Line Detector
When the circuit detects that a phone line has been cut, it activates a MOSFET which can be used to drive a relay, motor, etc. It can also be connected to a security system.
Telephone amplifier
While talking to a distant subscriber on telephone, quite often we feel frustrated when the voice of the distant subscriber is so faint that it is barely intelligible. To overcome the problem, circuit of an inexpensive amplifier is presented here. It can be assembled and tested easily.
Soft Musical Telephone Ringer
The normal telephone bell, at times (specially during night when one does not want to be disturbed), appears to be quite irritating. The circuit shown here converts the loud sounding bell into a soft and pleasing musical tone.
Phone Hold With Music
This circuit will allow you to place a phone call on hold and if you wish to have them listen to music while they are on hold.
Cellular Phone calling Detector
This circuit was designed to detect when a call is incoming in a cellular phone (even when the calling tone of the device is switched-off) by means of a flashing LED
Telephone line monitor
This nifty little circuit lets you record your phone conversations automatically
Ringing Phone Light Flasher
Makes your 220/110V bulb flashes when telephone rings. Can be very useful when you need silence, or just want to have strange phone :)
FM Telephone Bug
Extremely easy to build and very useful transmitter
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