Remote control using telephone

Posted on Feb 5, 2014

A teleremote circuit which enables switching on` and off` of appliances through telephone lines. It can be used to switch appliances from any distance, overcoming the limited range of infrared and radio remote controls. The circuit described here can be used to switch up to nine appliances (corresponding to the digits 1 through 9 of the te

Remote control using telephone
Click here to download the full size of the above Circuit.

lephone key-pad). The DTMF signals on telephone instrument are used as control signals. The digit 0` in DTMF mode is used to toggle between the appliance mode and normal telephone operation mode. Thus the telephone can be used to switch on or switch off the appliances also while being used for normal conversation. The circuit uses IC KT3170 (DTMF-to-BCD converter), 74154 (4-to-16-line demult-iplexer), and five CD4013 (D flip-flop) ICs. The working of the circuit is as follows. Once a call is established (after hearing ring-back tone), dial 0` in DTMF mode. IC1 decodes this as 1010, ` which is further demultiplexed by IC2 as output O10 (at pin 11) of IC2 (74154). The active low output of IC2, after inversion by an inverter gate of IC3 (CD4049), becomes logic 1. This is used to toggle flip-flop-1 (F/F-1) and relay RL1 is energised. Relay RL1 has two changeover contacts, RL1(a) and RL1(b). The energised RL1(a) contacts provide a 220-ohm loop across the telephone line while RL1(b) contacts inject a 10kHz tone on the line, which indicates to the caller that appliance mode has been selected. The 220-ohm loop on telephone line disconnects the ringer from the telephone line in the exchange. The line is now connected for appliance mode of operation. If digit 0` is not dialed (in DTMF) after establishing the call, the ring continues and the telephone can be used for normal conversation. After selection of the appliance mode of...

Leave Comment

characters left:

Related Circuits

  • New Circuits



    Popular Circuits

    Serial Servo Controller with Arduino
    Programming Cable for Kenwood
    USB FM Transmitter for MP3 Player
    Schematic Diagram Of LED Sequencer Based On The 555 Timer IC
    Economical Pump Controllers
    USB Cellphone Charger circuit
    Synchronous Dual Mode Phase Modulated Full Bridge Controllers
    Portable phone charger
    Interesting Wiring Schematic
    Trunk main wiring system diagram a formula
    XTR112 114 without external transistor circuit diagram