User Manual

Appendix A Technical Specifications
RFI-9256 Radio Modem User Manual Page 53 of 96
Figure 23: DB25 pin numbering
Pin Function DTE Function DCE Function
1 Data Terminal Ready (DTR) Output Input
2 Received Data (RX) Input Output
3 Transmitted Data (TX) Output Input
4 Data Carrier Detect (DCD) Input Output
5 Signal Ground (SG)
6 Data Set Ready (DSR) Input Output
7 Clear to Send (CTS) Input Output
8 Ready to Send (RTS) Output Input
9 Ring Indicator (RI) Input Output
Table 20: DB9 Pin Assignments
A.4 Back-to-back Repeater Connector
The connector used for a back-to-back repeater is shown in Table 21. Note that the main and auxiliary port
have been crossed to form a null modem cable (highlighted sections). All eight auxiliary I/O lines along with
synchronisation I/O are passed straight through.
Slave Pin Function Master Pin
1 +12V input
2 Transmit data out (TXD) main port 3
3 Receive data in (RXD) main port 2
4 Transmit data out (TXD) auxiliary port 5
5 Receive data in (RXD) auxiliary port 4
6 I/O control 7 6
7 I/O control 5 7
8 I/O control 0 8