Each 100-220V AC input is isolated by an optocoupler.
The data are read by a 18 pins PIC 16F88 which receives the commands and sends the data throught a RS232 DB9 port via a MAX232(or LT1081).
RS232 line parameters are 4800 bauds 8 bits, no-parity, 1 stop bit.
The protocole used to exchange RS232 frames is described here.
Schematics, components, part list and printed board are available in pdf format
Source code written in PIC assembler and Hex code are available and generated with MPLAB IDE.
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