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APPENDIX A: DB25 Pin Assignments
Appendix A: DB25 Pin Assignments
Desig- LCD
Pin nation Function Indicator Source
1 AA Frame ground—not connected
2 BA Transmit data (TD) TD DTE
3 BB Receive data (RD) RD Modem
4 CA Request to send (RTS) RS DTE
5 CB Clear to send (CTS) CS Modem
6 CC Data set (modem) ready (DSR) MR Modem
7 AB Signal Ground (SG) Ground
8 CF Carrier Detect (CD) CD Modem
9 +P Testing voltage, +10V Modem
10 -P Testing Voltage - 10V Modem
15 DB Transmit Clock (TC) Modem
17 DD Receive Clock (RC) Modem
18 CN Analog loopback (ALB) control
1
DTE
20 CD Data terminal ready (DTR) TR DTE
21 CN Remote digital loopback (RDL) control
1
DTE
22 CE Ring Indicator (RI) R Modem
23 CH Speed Select (CH/CI)
2
DTE
24 DA External transmist clock DTE
25 CN Test mode indicator (TM)
3
TM Modem
1
+voltage activates indicated loopback test (only if ALB-DTE controled
or RDL-DTE controled option is enabled); -voltage disables test.
2
+voltage, 14,400 bps; -voltage, 2400 bps.
3
Alternatively, pin 25 may be used for analog loopback (ALB) control.
See Appendix D.