54 TX3 Telephone Access System Installation and Operation Manual Version 5.4
LT-969 Copyright 2019
Lobby Control Unit Setup
4.2.4 RS-485
An RS-485 terminal lets you easily connect multiple telephone, card access and
elevator restriction controllers across a network. The RS-485 connection is
situated at the bottom middle of the main controller board and consists of two
separate terminals, each for an input and output. See figure 32.
Connect the RS-485 input terminal to the RS-485 output terminal of another
controller. See figure 32.
If you do not have end-of-line 120 Ω resistors, close JW5 on the first and last
controllers instead. See section 4.1.4 on page 50.
If there are problems with RS-485 communication, close both JW9 and JW10 on
either the first or last controller connected by RS-485.
Note: Use twisted shielded pair.
Recommended cables:
• RS485 cables
• Belden 3109A RS-485, (4 pr) 22 AWG (7x30) or equivalent
• Belden 9842 RS-485, (2 pr) 24 AWG (7x32) or equivalent
• Belden 9841 RS-485, (1 pr) 24 AWG (7x32) or equivalent
• CAT5 Cables
• Belden 72001E ETHERNET Cat 5e 2 Pair, 24 AWG or equivalent
• Belden 70006E Cat 5e, 100Mb/s, Quad, AWG 22 (1) or equivalent
Maximum total length:
• 4000 feet (1244 m) for 22 AWG
• 2500 feet (762.5 m) for 24 AWG
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