Cabling printers

Functions on the PC side of serial printer cables

FG (Frame Ground reference pin)
It is not necessary for you to use this pin, and using the pin can cause ground loop problems if the PC and printer are connected to different power sources. You have a Frame Ground pin only on a 25-pin connector, and it uses Pin 1.
TXD (Transmit Data output pin)
The PC sends data (the print job) through this pin which connects to Pin 3 on the printer. The PC uses Pin 3 on a 9-pin connector and Pin 2 on a 25-pin connector. This attaches the PC's transmit pin to the printer's receive pin.
RXD (Receive Data input pin)
The PC receives XON/XOFF characters through this pin, which connects to Pin 2 on the printer. The PC uses Pin 2 on a 9-pin connector and Pin 3 on a 25-pin connector. This attaches the printer's transmit pin to the PC's receive pin.
RTS (Request To Send output pin)
NetWare print services sets the signal level high for this pin (and the DTR pin) on the PC and keeps it in that state. The PC uses Pin 7 on a 9-pin connector and Pin 4 on a 25-pin connector. This signal can be used as a source for a high signal level to enable certain functions on some printers. If your printer cable connects this pin to a pin on the printer that requires a high signal level, printing will function properly. You can achieve the same results by following the steps in note 12.
NOTE: Early versions of NetWare print services set the signal level high on this pin when sending data and set the signal level low when not sending data. The timing of the signal changes caused many problems with printers that require a high signal level for data input. Beginning with version 1.22R, NetWare Print Services constantly maintains a high signal level for this pin.
CTS (Clear To Send input pin)
NetWare print services uses this pin for its hardware handshaking. The PC uses Pin 8 on a 9-pin connector and Pin 5 on a 25-pin connector. This pin connects to the pin on the printer that controls the flow of data. This is generally pin 20 on the printer, but some printer vendors use other pins (see note 14). If the signal level is high for this pin, data will be sent to the printer. Data is not sent when the signal level is low.
NOTE: If this signal level stays low for about 10 seconds while servicing a print job, NetWare print services reports an ``off-line'' condition.
DSR (Data Set Ready input pin)
NetWare print services does not use this pin. Other print services may require a high signal level for both Pins 5 and 6 on the PC for proper data flow control. It is recommended that you tie (solder) Pins 5 and 6 together to provide printing compatibility for other print services.
SG (Signal Ground reference pin)
NetWare print services uses this pin to provide a reference for signal levels. The PC uses Pin 5 on a 9-pin connector and Pin 7 on a 25-pin connector. The printer uses Pin 7.
DCD (Data Carrier Detect input pin)
Some PCs may require a high signal level on this pin to enable the PC to receive data from the printer. The XON/XOFF protocol will not function correctly with a low signal level. If you do not use the XON/XOFF protocol, the signal level on this pin can be high or low. The PC uses Pin 1 on a 9-pin connector and Pin 8 on a 25-pin connector.
It is recommended that you maintain a high signal level on this pin by tying (soldering) it to another pin that has a high signal level. Tie Pin 1 on a 9-pin connector to either Pin 7 or Pin 4. Tie Pin 8 on a 25-pin connector to Pin 4 or Pin 20.
DTR (Data Terminal Ready output pin)
NetWare print services sets the signal level high for this pin (and the RTS pin) on the PC and keeps it in that state. The PC uses Pin 4 on a 9-pin connector and Pin 20 on a 25-pin connector. This signal can be used as a source for a high signal level to enable certain functions on some printers. If your printer cable connects this pin to a pin on the printer that requires a high signal level, printing will function properly. You can achieve the same results by following the steps in note 12.
NOTE: Early versions of NetWare print services set the signal level high on this pin when sending data and set the signal level low when not sending data. The timing of the signal changes caused many problems with printers that require a high signal level for data input. Beginning with version 1.22R, NetWare Print Services constantly maintains a high signal level for this pin.