
Audio International, Inc. PA-480-01-x Installation Manual
Document # 540241, Rev IR, 04/2002 Page 8 of 15
3.4 Wiring Requirements
3.4.1 Introduction
The installing agency shall supply and fabricate all external cables
and mating connectors. The length and routing of external cables
should be carefully studied and planned before attempting
installation of the equipment. Allow adequate space for installation
of cable and connectors. Avoid sharp bends and placing cables
near aircraft control cables. Maintain a MINIMUM clearance of
three (3) inches from any control cable. If wiring is run parallel to
combustible fluid or oxygen lines, maintain a separation of six (6)
inches between the lines.
3.4.2 Power Wires
All power and ground wires shall be 16 AWG, MINIMUM shielded
twisted pair with the shield properly bonded at one end only. Power
ground wires shall be bonded to electrically conductive chassis
mounting point with <1 Ωresistance or <50 Ωimpedance. Twisted
shielded cable shall be in accordance with MIL-W-27500 or
equivalent. Additionally, ensure that the chassis grounding post is
bonded to aircraft frame with <1 Ωresistance or <50 Ωimpedance.
Protect power wires with circuit breakers or fuses located close to
the electrical power source bus.
3.4.3 Audio Wires
All audio input cables should be 22 AWG, MINIMUM, shielded
twisted pair. All output cables should be 16 AWG, MINIMUM
shielded twisted pair. Twisted shielded cable shall be in accordance
with MIL-W-27500 or equivalent.
3.4.4 Data Bus Lines
3.4.4.1 All data bus connections require twisted shielded cable
with the cable shields properly grounded. Twisted shielded
cable must be in accordance with MIL-W-27500 or
equivalent. The wire size for the conductors in this cable is
to be 22 AWG MINIMUM. The shield is to be connected
wherever a shield pin is provided. Shield terminations are
to be made as close to the connector pin as possible. In
the event shield pins are not utilized, the data bus shield
must be terminated per AI’s RS-485 specification. AI’s
RS-485 serial data bus specification is available upon
request.