Cloud Electronics MPA626 - Manual (Page 8)

MPA-626: Installation and Operation Manual 7
3. Restoration Relays
The MPA-626 has two restoration relays one activated by Mic 1 access, the other by Mic 2
access. See section 7.3
When the microphone input(s) are to be used without the access feature the microphone
access connector must be fitted with two shorting links, one from 0V to 1 and another from 0V
to 2. The rear panel priority switch must also be in the 'out' position. These settings will ensure
that both microphone channels are open at all times.
7.3 Restoration Relays
There are two restoration relays; one activated by mic 1 access the other by mic 2
access. Whilst the relay contacts are intended for use in restoration in line speaker
systems, the contact ratings are adequate to enable them to switch the low impedance
outputs. All of the relay contacts have been made available on the rear panel connector,
enabling the MPA-626 to work with either 3 wire or 4 wire restoration systems.
A 24V d.c supply is provided for 4 wire systems. The 24V supply is protected by means
of a 0.4A PTC type thermal fuse, which can be reset by switching off the unit for 15
seconds. In the diagram below the paging microphones are shown with a shorting
switch across the microphone, this is a common feature in such microphones but is not
a requirement with the MPA-626 as the unit contains circuitry that mutes the
microphone inputs when they are not accessed.
Example of a 4-Wire Restoration System.
Example of a 3-Wire Restoration System
11-07-02 V4