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To enable RS-485 termination, install jumper on pin header J22 (on the last unit on the communication line).
Notes:
The (EIA) Electronic Industries Association standard defines RS-485 as an electrical interface
for multi-port communications on a bus transmission line. It allows for high-speed data
transfer over extended distances (4000 feet [1219m]). The RS-485 interface uses a balance of
differential transmitter/receiver to reject common mode noise. For increased reliability over
the extended distances, End-Of-Line (EOL) termination is required.
RS-485 must be terminated at both ends of the RS-485 line (bus). Terminating the line
provides a more reliable communication by minimizing the signal reflection and external noise
coupling. Each component provided has an on-board terminator. The installer should
determine which device is at the end of the communication line.
50.4
Control Output Wiring
Contact protection circuit must be used. The following two circuits are recommended. Locate the protection
circuit as close to the load as possible (within 12 inches [30cm]), as the effectiveness of the circuit will
decrease if it is located further away.
ICM upstream wiring
Hardware Installation Guide
293
revision 7 —
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