Telephone related electronic circuits

This project is aimed to make the low cost intercom system by which eight telephone lines can be interfaced with this hardware.... [read]

Many a times one needs an extra telephone ringer in an ad joining room to know if there is an incoming call.... [read]

Many a times one needs an ex- tra telephone ringer in an ad- joining room to know if there is an incoming call.... [read]

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... [read]

This circuit enables automatic switching-on of the tape recorder when the handset is lifted.... [read]

Here is a simple circuit which can be used with cordless phone SANYO CLT-420 or similar sets.... [read]

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... [read]

Extremely easy to build and very useful transmitter... [read]

Often a need arises for connection of two telephone instruments in parallel to one line. But it creates quite a few problems in their proper performance, such... [read]

This add-on device for telephones can be connected in parallel to the telephone instrument. The circuit provides audio-visual indication of on-hook, off-hook,... [read]

Here is a simple yet very useful circuit which can be used to eavesdrop on a telephone conversation. The circuit can also be used as a wireless telephone amplifier.... [read]

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.... [read]

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.... [read]

Makes your 220/110V bulb flashes when telephone rings. Can be very useful when you need silence, or just want to have strange phone :)... [read]

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... [read]

The circuit shown here is used to switch on a lamp when the telephone rings, if the ambient light is insufficient.... [read]

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... [read]

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.... [read]

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... [read]

In this circuit, a simple calculator, in conjunction with a COB (chip-on-board) from an analogue quartz clock, is used to make a telephone call meter. The... [read]

Acompact, inexpensive and low component count telecom head- set can be constructed using two readily available transistors and a few other electronic components.... [read]

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... [read]

Telephone In-Use Relay Controller circuit diagram... [read]

Very often when enjoying music or watching TV at high audio level, we may not be able to hear a telephone ring and thus miss an important incoming phone call.... [read]

This nifty little circuit lets you record your phone conversations automatically... [read]

Here is a telephone line vigilant circuit to guard against misuse of your telephone lines. It monitors telephone lines round the clock and provides visual... [read]

The given circuit, when connected in parallel to a telephone, dis- plays the number dialled from the telephone set using the DTMF mode. This circuit can also... [read]

Using modulated rectangular waves of different time periods, The circuit presented here produces ringing tones similar to those produced by a telephone. The... [read]

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... [read]