Epson C82307/08 (Serial I/F User Manual page 22

TRB (pin No. 11, 13) in the case of RS-422A, and from
RS-232D: negative EIA
RS-422A: negative EIA
level
20-mA Current Loop: low
RS-232D: positive EIA
RS-422A: positive EIA
20-mA Current Loop: high
DTR Handshaking
TRA-TRB,
TRA: inverted
TRB: noninverted
TRA-TRB
TRA: inverted
TRB: noninverted
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