User's Manual

3.3. Serial I/O Connector
The 9-pin serial I/O connector is a female 9-p D-subminiature connector
having the following pins configuration.
Front-view of DB-9 connector on modem (female)
Pin # Name Dir Function Level / Specification
1 CD out Carrier detect If enabled, indicates presence of carrier. 0
means carrier is present. If disabled, it is
asserted (0) whenever the modem is
operational, and not in the configuration
mode. It will be a 1 when the modem is in
the configuration mode.
2 RxD out Receive data Data out of the modem.
3 TxD in Transmit data Data into the modem.
4 DTR in Data terminal ready Normally ignored by the FireLine modem.
5 GND Ground connection Signal and power ground
6 DSR
out
Data Set Ready
Normally is set to 0 when modem is
powered on.
7 RTS
in
Request to send
Used to stop/start the flow of data coming
out of the modem TxD pin. 0 = OK to send,
1 = don’t send. Leave disconnected if not
used.
8 CTS
out
Clear to send
Used to stop the flow of data going into the
RxD pin from the device connected to the
FireLine. 0 = OK to send, 1 = don’t send. If
the FireLine cannot accept more data, it will
negate this signal (set to a 1).
9 Power
In/out DC power (not Ring
signal)
User may supply the DC power to the
modem on this pin.
Note: RS-232 signals use positive and negative voltages to represent digital 1s and 0s. A positive
voltage is a 0, and a negative voltage is a digital 1.
This pin-out allows it to be directly plugged into a computer’s 9-pin serial port
using a conventional 9-pin RS-232 serial cable. To connect it to a modem, or
computer peripheral that has a serial port, you will need a “null-modem”
cable. See Appendix A for more information on wiring a null-modem cable.