General Rs-485 Bus Installation - EverFocus PARAGON Series Instruction Manual

2.4.1 General RS-485 bus installation

The EKB-500 keyboard uses an RS-485 simplex wiring; the signal is transferred via a single twisted pair
line. CAT5 network cable is recommended, UPT version (unshielded) is sufficient for normal application. A
shielded cable should be used if the installed cables are expected to be highly susceptible to interferences.
The number of devices installed in one bus is limited to 32, and the maximum cable length is 1200m. Both
of these can be expanded using a signal distributor (see below).
Both the first and the last device in series should be terminated with 120 Ohm resistance in order to
minimize line reflections.
RS-485 bus serial wiring
When using connector boxes, cable length from box to device should be limited to 2m.
RS-485 bus serial wiring with connector boxes and connection cable
A direct RS-485 bus star wiring is not supported unless using a signal distributor (see below).
Improper RS-485 bus star wiring
An RS-485 signal distributor may be used to use a star wiring configuration.
Star wiring with RS-485 signal distributor
16