User Manual

Company Confidential 30 Raveon Technologies Corp.
(DB-9 Female shown. Same wiring for male-to-male cable)
Connector 1 Connector 2 Function
2 3 Rx Tx
3 2 Tx Rx
4 6 DTR DSR
5 5 Signal ground
6 4 DSR DTR
7 8 RTS CTS
8 7 CTS RTS
Compatibility issues
The null modem cable with full handshaking does not permit the older way of
flow control to take place. The main incompatibility is the cross connection of
the RTS and CTS pins. Originally, these pins are used for a question/answer
type of flow control. When the full handshaking null modem cable is used,
there is no request anymore. The lines are purely used for telling the other
side if communication is possible.
The main advantage of this cable is, that there are two signaling lines in each
direction. Both the RTS and DTR outputs can be used to send flow control
information to the other device. This makes it possible to achieve high
communication speeds with this type of null modem cable, provided that the
system has been designed for it.