TA Triumph-Adler LP 4024 - Manual (Page 209)

Serial Interface
C-5
C.2 Serial Interface
C.2.1 Interface Signals
The pins of the printer's RS-232C interface connector carry the signals
listed in the table below. The table also indicates whether each signal is
incoming or outgoing with respect to the printer.
RS-232C Signal Pin Assignment
Brief descriptions of the signals follow.
FG - Frame Ground - (Pin 1)
This pin is connected directly to the printer frame.
TXD - Transmit Data - (Pin 2)
This output carries asynchronous data sent by the printer to the computer.
It is used mainly in handshaking protocols.
RXD - Receive Data - (Pin 3)
This input carries serial asynchronous data sent by the computer to the
printer.
RTS - Request To Send - (Pin 4)
This output is always held high (above 3 volts).
CTS - Clear To Send - (Pin 5)
DSR - Data Set Ready - (Pin 6)
Unused.
SG - Signal Ground - (Pin 7)
All signals can transmit between the printer and the host computer to send
each signal with a signal ground.
Pin In/out Signal Description
1 - FG Frame ground
2 Out TXD Transmit Data
3 In RXD Receive Data
4 Out RTS Request To Send
5 In CTS Clear To Send
6 In DSR Data Set Ready
7 - SG Signal Ground
20 Out DTR Data Terminal Ready