Operation Of The 9131D - Optelecom-nkf 9131DT Installation And Operation Manual

RS485, RS422, AND MANCHESTER TERMINATION RULES
For RS422, RS485, and Manchester connections it is possible that multiple devices may be connected in
parallel. This is usually a transmitter and many receivers connected together or many transceivers in RS485.
When this occurs, this parallel bus must be terminated with the correct impedance. Use the following rules
to determine if the termination resistors should be enabled or disabled.
RS422 and RS485
Enable termination only on the device farthest from the transmitting end, leaving the input termination
disabled on the devices in between.
Manchester
If there are six or more devices, disable all the termination resistors. If there are fewer than six devices,
enable termination only on the device farthest from the transmitting end, leaving the input termination
disabled on the devices in between.

Operation of the 9131D

Operation is straightforward. Connect per the directions in the Configuration and Connection Guide section
on page 5. There are no adjustments. Under normal operation, only the green POWER indicator on the
9131DT and the green SYNC indicator on the 9131DR will be illuminated.
8