BayTech 24SII Owner's Manual page 39

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IMPORTANT: Before you proceed with cabling, you must know
whether the devices to which you will connect the Model 24SII DES
are DTE (Data Terminal Equipment) or DCE (Data Communication
Equipment). The following devices are generally DTE: terminals,
printers, computers like the IBM PC. The following devices are DCE:
modems and some computers.
If your device transmits data on Pin 2 or receives data on Pin 3, it is
DTE. If your device receives data on Pin 2 and transmits data on Pin
3, it is DCE. However, to verify the interface requirements, please
refer to the Owner's Manual for your device.
The serial ports on the M24SII-V04 I/O module has DB-25 female
DCE connectors and use the following signals for communication:
PIN# EIA-232
1 PGND
2 TX
3 RX
4 RTS
5 CTS
6 DSR
7 SGND
20 DTR
DCE PORT SIGNALS
DIRECTION DESCRIPTION
---- Protective ground
Input Data in
Output Data out
Input Internally enabled if no wire connected
(normally not used).
Output -12V when DCE device's buffer is full.
Output +12V when DCE device powers-up.
---- Signal ground
Input Transmit enabled when +12 V.