CyberResearch RS-232 - Manual (Page 14)

COMT 366 Series CyberResearch
®
Serial Communications
6 ©Copyright 2001 CyberResearch, Inc.
4.1 Termination of the Line
There are four user-selectable resistive terminating values which are implemented using
switches A and B of the dipswitch. As the length of the transmission cable and the
number of users increases, the chosen value becomes more critical to error-free operation.
Typically, devices at the end of a long bus are terminated and units multi-dropped
between the ends are not terminated. The cable used to connect devices off the long bus
should be kept as short as possible. The value chosen should match the characteristic
impedance of the twisted pair being used. The termination value can be selected using the
following table
Switch Termination Value
1 2 OHMS
Off Off None
On Off 200
Off On 120
On On 75