PSI-MODEMSHDSL/SERIAL
2-10
PHOENIX CONTACT
104275_en_c00
RS-232 interface
The RS-232 interface is a 9-pos. D-SUB plug. All signals except for the RI (Ring Indicator)
signal are present.
The interface has ground reference and is not electrically isolated from the potential of the
supply voltage.
Automatic DCE/DTE switchover (RS-232)
The modem automatically detects whether a DCE or DTE device is connected to the RS-
232 interface. The advantage of this is that cabling is easier. However, this can lead to prob-
lems in some special cases.
–
If two SHDSL devices are connected via a single RS-232 cable, automatic DCE/DTE
detection must be disabled on one of the devices.
–
If the third-party device switches between DCE and DTE during operation (e.g., be-
cause a switch has been actuated), the modem does not detect this change. The same
is true when a cable that can be switched is switched.
In this case, the serial cable must be disconnected from the SHDSL modem and
plugged back in again.
We recommend using shielded data cables.
For devices that are connected to the
RS-232
interfaces, the modem automatically
switches between DCE and DTE by default.
Table 2-1
Assignment of the RS-232 interface (D-SUB)
Contact
Signal
Comment
Assignment
1
DCD
Data carrier detect
2
TxD
Transmit
3
RxD
Receive
4
DTR
Data terminal ready
5
GND
Signal ground
6
DSR
Data set ready
7
CTS
Clear to send
8
RTS
Request to send
9
–
1
5
6
9