Service manual

34
Theory of Operation
DCB, DCFCB and DCFCTB Models
are all normally open with contact ratings up to 5 Amps and 240 Volts AC RMS. K3
and K4 outputs have selectable No or NC contacts.
Speaker Output Section
The microprocessor (U13) generates warning sounds on pin 17, which are routed out
thru amplifier U10 to the speaker output JP2.
Serial and I
2
C Ports
Transmit serial data from pin 3 of the micro (U15) goes to U11 - pin 7, which
converts the TTL level to +/- 12 volts RS232 levels and passes the transmit data to
serial port JP8. Receive data from JP8 is likewise converted from RS232 levels to
TTL levels and sent to the micro on pin 2.