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ERS-4 Instruction Manual
2.4 RS-485 KEYBOARD / PTZ INSTALLATION
The ERS-4 provides an RS-485 interface for PTZ control of speed domes and other PTZ devices.
Furthermore the ERS-4 can be remote-controlled by the EKB-500 universal keyboard. 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
The ERS-4 uses a RS-485 simplex wiring; the signal is transferred via a single twisted pair line. CAT5
network cable is recommended, UTP 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
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
A direct RS-485 bus star wiring is not supported unless using a signal distributor (see below).
Improper RS-485 bus star wiring
A RS-485 signal distributor may be used to use a star wiring configuration.
Star wiring with RS-485 signal distributor
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