Chapter 2
Installation
13
Twisted-pair connections
The twisted-pair connections are available to connect additional devices or for existing installations where
individual wires were used to connect to the old phone-style I/O box. Easy-to-use RJ-cable connections are
also available on the new I/O box. See RJ-cable connections on page 12.
Adhere to all installation guidelines while making connections, including your local codes and those provided
in Installation guidelines on page 8.
Figure 8. Wire connections to the I/O box
Bias switch
The bias switch maintains an appropriate load on the RS-485 line. Set the bias switch to ON for one
keypad in a typical system (any one keypad and only one keypad). If your system is divided into
groups that are separated by fiber or Ethernet bridges, you must set the bias switch to ON for one
keypad in each group.
Tie-wrap
For safety, use a tie-wrap
to secure the power cable
to the tie-in.
Observe polarity for:
•12VDC
•RS-422
•RS-485
Earth ground (to ground)
RS-422 IN (from keypad or
alarm unit, if used)
Speaker/shield (to remote
speaker, if used)
* For mux, DVMRe, or additional keypad I/O box. (RS-485
connections are also available with the RJ45 connectors.)
RS-485 connection*
RS-422 OUT (to switcher
or cameras)
12 VDC power
(12 VDC transformer must
have a positive center
polarity plug
)
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