OKIDATA Pacemark 3410 Service Manual page 31

RS232-C Serial Interface
When the interface select switch is turned ON, the serial interface is selected and Q5 is in the serial
interface mode.
The RS232-C interface signals (DSR, CTS, CD and RD) are converted to TTL levels by the line receiver
(Q13) and input to Q5 where the serial data is converted to parallel data.
The interface signals (DTR, RTS, SSD and TD) output from Q5 are converted from TTL levels to
RS232-C levels by the line driver (Q12) and sent to the serial interface connector.
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