EverFocus EDR-1640 - Manual (Page 19)

2.4 RS-485 keyboard installation
All EDR920/1640 functions can be remote-controlled by the EKB 500 universal keyboard. Using
the EEPbus protocol, digital video recorders, keyboards and speed domes can be installed on
one single RS-485 bus. One system can comprise up to 8 keyboards.
2.4.1 General RS-485 bus installation
EKB-500 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 (expandable through signal
distributors).
Basically, the bus should be created by serial wiring, star wiring is only permitted using signal
distributors.
Maximum RS-485 bus cable length is 1200 m. Both the first and the last device are normally
120 Ohm terminated in order to minimize line reflexions.
RS-485 bus serial wiring
Cable length from box to device („Stubs“) has to be limited to 2m using connector boxes.
RS-485 bus serial wiring with connector boxes and connection cable
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