Notifier AFP-400, Руководство по установке

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4-34 AFP-400 Installation
PN 50253:A2 03/12/96
ACT-1 Audio Coupling Transformer
MPS-400
MPS-400
CPU-400
TB4
Remote Cabinet
Main Cabinet
Remote
Annunciator
The ACT-1 Audio Coupling Transformer couples low-level audio to audio
amplifiers or other audio inputs, such as the ATG-2. An ACT-1 can be used
to couple a low-level audio signal to up to eight devices in the same cabinet.
It provides electrical isolation between low level audio riser and equipment
to which the signal is to be fed (amplifiers or the ATG-2). Also, the ACT-1
provides common mode noise rejection (CMNR), greatly reducing crosstalk
from signaling line circuits.
You can install the ACT-1 in any application that uses AA-30 or AA-120 audio
amplifiers, subject to the following restrictions:
• The amplifiers must mount remotely from the source of low level audio
devices, such as an AMG or ATG.
• The power supplies in the main control panel cabinet and the remote
cabinets must share the same common.
• Ground fault is enabled on each power supply.
Isolated power supplies, each with respective ground fault detection circuits
enabled, are often used to aid the quick location of ground faults in large
systems. This task is more difficult if the entire system (main and all remote
devices) share the same common and the power supply in the main control
panel cabinet provides ground fault detection.
In larger systems, capacitance becomes a critical factor in creating sporadic
and difficult-to-find ground faults along a single common connection. In
these systems—as in systems that expand—use an ACT-1 if possible.
For example, a system consisting of a remote annunciator powered from a
local supply within the same cabinet—but connected through an EIA-485
circuit—to the main control panel. (See the figure below.) A common
connection occurs (although a poor one) along the EIA-485 interface.
Therefore the supplies in this system are not adequately isolated and
problems will occur. In this case, the earth fault detection of the remote
power supply must be disabled and a good common connection must be
made between the two systems.
An ACT-1 is not required for amplifiers mounted in this remote cabinet but
installation of an ACT-1 can reduce CMN from the SLC loop.
Isolating Power Supplies
Overview
Remote Annunciator Powered from a Local Power Supply