Coax Control; Rs485 Twisted-Pair Telemetry - Honeywell ACUIX Installation And Configuration Manual

Installation Preparation

Coax Control

RS485 Twisted-Pair Telemetry

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The ACUIX domes support telemetry control over coaxial cable. The dome must be set to
VCL UTC for coaxial telemetry.
Up-the-coax operation of up to 1000 feet (300 meters) is possible with the appropriate
coaxial cable.
Caution
• Star wiring configurations are acceptable with the use of a code
distribution unit such as Honeywell HDCD8TP.
• Always keep RS485 data cables away from all other cables and run
them in complete isolation whenever possible.
• Couple all data cable shields to data ground at the control point end
only. The cable shields should not be connected at any other point.
• Connect the cable shield at the controller and connect the cable shield
through any junction boxes installed, but do not connect the cable
shield to the dome.
When using RS485 twisted-pair telemetry, the video signal is transmitted via a coaxial or
CAT5 twisted pair cable and the control data (telemetry) information is a twisted-pair
cable.
RS485 twisted-pair telemetry cabling is installed and wired as a network that consists of
one or more daisychains. When more than one daisychain is installed, an RS485
telemetry distribution unit must be installed to broadcast telemetry data across the entire
RS485 network. Multiple distribution units can be installed on the RS485 network to allow
for complex wiring arrangements.
Most RS485 cable is 24 AWG—a 20-gauge unshielded twisted pair (UTP) cable is
recommended. The UTP cable is a single twisted-pair with an overall shield and can be
used in a daisychain up to a maximum of 4000 feet (1219 meters). These cables are
available in a series of overall outer sheaths from standard internal usage finishes to
external containment and direct burial types and must have less than 20 pF/ft (picorfarads
per foot) of mutual pair capacitance (capacitance between the two conductors in one
pair). The mutual pair capacitance should be uniform throughout the length of the cable.