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Using DTMF encoding and decoding wireless calling implement

2016-11-07 11:48  
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Using DTMF encoding and decoding wireless calling implement circuit diagram
Using DTMF encoding and decoding wireless calling implement circuit diagram
The wireless calling implement is composed of calling implement and the host. The two parts use DTMF encoder pulse to realise communication. Different calling implement has different codes only, the circuits are all the same. The calling implement is shown in figure 1. IC2 is the DTMF encoding specific integrated circuit (telephone dial tone can also be integrated circuits), which has four southbound R1 ~ R4, C1 ~ C4 line of four columns, external standard 4 × 4 matrix keyboard. It produces 16 different encoding. When any key is pressed, a row line and a column line are connected. Then the output pin corresponding to the end TONE tone pulses. It uses optocoupler number keys as the icon to connect to 1 # key. IC3 serial data of the long-wave radio transmitter module, which uses 150kHz carrier frequency, a strong anti-interference ability. IC2 pin dual audio pulses emitted modulated carrier out by the antenna.