The main components of this circuit ICl is a new digital pulse signal transmission line carrier modulation / demodulation IC SST8803, it has low power consumption , high sensitivity, anti-jamming and anti-static performance and good features , single to complete the data signal modulation Send and receive all of demodulating the work . Can make use of low-voltage power lines , radio lines and closed-circuit television signal lines for vector data , information exchange, can be used for remote telemetry , centralized alarm , paging and multi- computer network systems. Figure (a) the typical application circuit for the SST8803 . ICl ‘s ?, ? feet for the positive and negative power supply terminal , the voltage limit value plus a minimum -0.3V, maximum 6.5V. ? pin is the reference voltage output , VREF = VDD / 2, ? feet for the external filter capacitor C11 . 11,12 pin internal circuits and quartz crystal X1 455kHz clock signal generated for the signal modulation or demodulation . 15 foot working model for the selection side , plus low modulation transmitter state at the time , Canada is high at the time of receiving and demodulating the state , half-duplex communication can be easily achieved . R7, C7, VD2 up the automatic reset circuit . VDl is 6.5V limit voltage protection control , the power generated transient high-voltage circuit is not damaged when the guarantee . Figure (b) is SST8803 and digital encoder / decoder is connected instance. IC2 is compatible with digital signal encoding and decoding devices UM3758-108A, the clock frequency f = l/0.5Rs · Cs, the circuit to take f = 160kHz. IC2 ? ~ ? foot tri-state address code is input , the maximum capacity of 310 address code = 59049 . IC211 ~ 18 feet for data input ( encoding ) / output ( decoding ) side , which is an 8-bit parallel port . Sl is the mode selector switch , encoding IC2 21 feet is high , by the CD4069 inverter IC3-1 after RP , ICl 15 pin is low ( modulation state) , encoded data stream from the IC2 23 foot string Line output to ICl 5 feet , sent to the grid modulated ; decoding IC2 21 feet for the low , IC1 15 feet was high ( demodulation state) , demodulated digital signal sent by the IC1 17 feet IC2 22 feet , after decoding by the IC2 11 ~ 18 feet out . At this point IC2 ‘s . Connected with the light-emitting diode LEDl feet , if the input signal is valid, IC2 23 pin outputs a low signal to drive LEDl shiny look , as a successful symbol decoding receiver .