KTI Networks KSC-240, Installation Manual

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SW1-8&7
BIAS-D RS-485/422 receiver line bias is disabled
BIAS-E RS-485/422 receiver line bias is enabled
The line bias is used to maintain the proper idle-state voltage to the idle
condition (when no driver is enabled on the bus). These bias resistors are
pull-up resistors on the data B line and pull-down resistors (to ground)
on data A line. In 4-wire configuration, the bias resistors are placed on the
receiver lines. [BIAS-D] disables the internal BIAS resistors on receiver
lines.
[BIAS-E] setting enables internal bias resistors. The bias configuration
can support up to 30 receiver nodes with no terminators. If the bias
configuration is not proper for your physical topology, set to [BIAS-D]
and use external bias design according to your application.