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# Using telephone remote control principle explanation

2015-03-03 00:46
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This article is to use the telephone remote control principle explanation. By convention, in order to better grasp the principles you are, we recommend you to combine text read schematics. This circuit can be used to switch to nine electrical (numbers 1 to 9 corresponding to the telephone keypad). DTMF signal as a control signal the telephone instrument. This figure "0 'in DTMF mode for the device to switch between modes and normal telephone operation mode, so the phone can be used to turn on or turn off appliances also be used for normal conversation. Circuit uses IC KT3170 (dtmf to bcd converter), 74154 (4 to 16 lines demult-iplexer) and five CD4013 (D flip-flop) ICs. working circuit as soon as the establishment of a call (hear the call back tone), dial "0" in the DTMF mode. This is the "decoder IC1 1010 ', further demultiplexed by IC2 O10 output (at pin 11) IC2 (74154). Active low output IC2, after inversion by the inverter gate IC3 (CD4049 ), a logic 1 This is used to toggle flip-flop 1 (F / F - 1) and relay RL1 full of vitality. Relay RL1 has two conversion contacts, RL1 RL1 (a) and (b). (a) the vitality of the RL1 contacts provides a 220 ohm loop across the telephone line while RL1 (b) contacts 10 khz tone injection line, which indicates to the caller, electrical mode is selected, 220 - ohm loop disconnect the telephone line from the telephone line rings exchanged. now The wire is connected to the operating mode if the number "0" Do not dial (DTMF) in the establishment of the call, the ring continues and the telephone can be used in normal conversation. When choosing the operating mode, if the number '1 'is set aside, it is decoded by IC1, its output is 0001'. This code is then multiplexed to the 4-16 BCD line signal splitter corresponding output of IC2, the inversion of the inverter gate CD4049, go to a logic 1 state. This pulse switches to the standby state corresponding trigger. This flip-flop output is used to drive a relay (RL2 on), you can turn on or turn off the electrical connection through its contacts. Dial other digits in a similar manner, other equipment can be switched "on" or "off." Once the switch operating over, 220 - 10 khz ohm loop resistance and tone telephone line needs to be removed. To achieve this goal, the figure "0 '(DTMF mode) is dialed again to toggle flip-flop a disconnect relay RL1, terminate the loop line and the 10 khz tone is also disconnected the telephone line is thus released again to receive normal calls This circuit is connected in parallel to the telephone instrument.
If you are a first reading on this principle, we recommend that you carefully read several times in order to better fully grasp this simple but effective circuit.

Remote control using telephone

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