External Modem Connection
Modem
To RS-232C port (25-pin)
To CO line/PBX extension port
assigned as the CO line destination RS-232C Port
(9-pin)
External Modem (25-pin) PBX (9-pin)
Signal Name
RD (RXD)
SD (TXD)
ER (DTR)
DR (DSR)
Signal Name
RD (RXD)
SD (TXD)
ER (DTR)
DR (DSR)
Pin No.
2
3
4
6
Pin No.
3
2
20
6
CAUTION
To protect the system, keep the following in mind:
1. Make sure that both connector cases (frame ground) of the RS-232C straight cable (shielded cable)
are conductive. If they are not conductive, make sure that both connector cases of the cable are firmly
connected.
2. If this is not possible, connect the frame of the PBX to the frame of the external modem using a
grounding wire in order to prevent difference in the electrical potentials.
After connecting the PBX and the external modem, set the power switch of the external modem to "ON", then
the external modem will be initialized with the default values.
The following AT command settings may be required for the modem:
•The Data Terminal Ready (DTR) signal should be ignored.
•The Data Terminal Equipment (DTE)/Modem flow control should be turned off.
•Data compression should be disabled.
•Error Correction is not necessary.
Note
•An AT command (for initialization, enabling automatic answer, etc.) can only be programmed by
Maintenance Console. "AT&F" is stored as the default value.
•For more information about the AT command, refer to the external modem's instructions.
114 Installation Manual Document Version 2011-10
4.2.1 PC Connection