Installation manual

Section 3
Physical Installation
Source Equipment
AC Power
Use the Switched Outlet to provide power to source equipment whenever
possible, because the PX-700 needs to power up equipment in a known
state when the Audioaccess Installation comes on. In addition, when the
source equipment is shared with another audio system, the PX-700 needs
to control the equipment status so that it does not stop transports or power
off equipment in use by the other audio system (refer to Switched Outlet
on page 3.14).
Wire
Requirements
Audioaccess products must be interconnected for them to communicate over the
Audioaccess RS-485 bus. Controllers located close to each other (e.g. multiple
PX-700s) can be connected to the RS-485 bus using any type of 4-conductor,
24AWG cable. Keypads and Audioaccess products located more than 250 feet
from the head end have specific cable requirements impacting the number of
conductors required and type of cable used. Follow these guidelines:
1. Use cable constructed of twisted pairs with either stranded or solid con-
ductors. Twisted pairs reduce the effects of electrical noise induced on the
cable by ensuring the noise is ‘common mode’ (the same on both wires of
the pair), and therefore is ignored by the bus transceiver IC. Make sure
the data lines (DATA 1 and DATA 2) are a pair and power and ground
(PWR and GND) are a pair.
2. If you are using only KPS keypads, use cable with 2 pairs. For KP3
keypads, use cable with 3 pairs (see KP3 Wiring). For ATC keypads, use
Cat 5 (4 pair) cable (see ATC Wiring on page 3.4).
3. If your installation is in a high EMI environment (for example, subject to
frequent and/or severe electrical storms or in close proximity to a radio
transmitter), use only shielded, twisted pair cable regardless of the cable
length. For shielded cable to be effective, connect all shields together at
the head end and tie to earth ground (use one of the zinc plated [silver]
screws on the rear panel of the Controller near the Keypad connector).
The shield should not be connected at the keypad. Long outdoor runs of
cable should be in earth-grounded metal conduit.
4. Use cable with a wire gauge appropriate to the length of cable run from
the keypad (or product) to the Controller. There will be a voltage drop
3.1