8
External Interfaces
• Always connect the #5 SG (Signal Ground) of the PS-A unit to the connected device,
especially if the connected device is also not isolated. Failure to do so may damage
the RS-232C/RS-422/RS-485 circuit.
Serial Interface (COM1, COM2, COM3, COM4)
COM1, COM2, COM4
COM3
COM3 can be changed to either RS-232C,
RS-422 or RS-485. (The factory setting is
RS-232C.)
To change this setting, open the
PS-A unit's rear cover and set slide switch on
the circuit board to the desired position.
Please refer to "Switches" for details.
*2 To enable RTS automatic control of the TX output driver, set SW No. 9 and 10 ON, and set SW No.4
OFF.
To enable control of the TX output driver via RTS signals, set SW No. 9 and 10 OFF, and set SW
No.4 ON
*3 If you use the termination resistance, base your settings on the connection specifications.
Interfit Bracket
#4-40 (UNC)
Pin #
RS-232C
Signal Name
Description
1
CD
Carrier Detect
2
RD(RXD)
Receive Data
3
SD(TXD)
Send Data
4
ER(DTR)
Data Terminal Ready
5
GND
Signal Ground
6
DR(DSR)
Data Set Ready
7
RS(RTS)
Request to Send
8
CS(CTS)
Clear to Send
9
CI(RI)/+5V
*1
*1 To change the RI/+5V setting of #9 pin, open the
PS-A unit's rear cover and set slide switch to the
desired position.
Please refer to "Switches" for details.
Called status display
(Fixed “RI“ for COM4)
/
+5V Output
(Switching available)
FG
FG
Frame Ground
(Common with SG)
Pin #
RS-232C
Signal Name
Description
1
CD
Carrier Detect
2
RD(RXD)
Receive Data
3
SD(TXD)
Send Data
4
ER(DTR)
Data Terminal Ready
5
GND
Signal Ground
6
DR(DSR)
Data Set Ready
7
RS(RTS)
Request to Send
8
CS(CTS)
Clear to Send
9
CI(RI)
Called status display
FG
FG
Frame Ground
(Common with SG)
Pin #
RS-422
Signal Name
Description
1
RDA
Receive Data A (+)
2
RDB
Receive Data B (-)
3
SDA
Send Data A (+)
4
NC
No Connection
5
GND
Signal Ground
6
NC
No Connection
7
SDB
Send Data B (-)
8
NC
No Connection
9
NC
No Connection
FG
FG
Frame Ground
(Common with SG)
