70Appendix 3 Interface Specifications! RS-232C InterfaceDsub, 9-pin (female)Pin No. Signal Functions Signal IN/OUT2 SD (TXD) Send data Output3 RD (RXD) Receive data Input4 Short with pin 6 5 SG Signal ground 6 Short with pin 4 7 CS (CTS) Ready to send Input8 RS (RTS) Request to send Output! Interface circuitsOutput circuit Input circuitTXD, RTS RXD, CTSVoltage polarity Logical value Control level+ 0 (space) ON- 1 (mark) OFF
