As shown in FIG, D187 is a universal asynchronous receiver transmitter (UART), its RX/TX signal received optocoupler N21, the N22 and N29, so put the RS-485 communication inter
face receiver/transmitter D28 and microprocessor D211 is completely optically isolated up. D197 is a generator, currently set communication rate is 9600bit/s. D189 is another universal asynchronous receiver transmitter. Optocoupler N204 and N206 to the local RS-232 communication port and a microprocessor D211 completely isolated. D209 is a single isolated 5V power supply is converted into a dedicated RS-232 driver chip for l2V communication.