ISP Technologies HDDS Master Control Module - Manual (Page 6)

Principles of the Master Control Module operation:
Each of the six zones of the Master control Module allow input of a balanced audio
signal and a front panel Master Level Control for each zone. As can be seen in the
previous block diagram all level control is provided by a voltage controlled amplifier.
The VCA output is followed by a differential line driver which drives the outputs A, B
and C on the rear panel of the Master Control Module. Each output A, B and C combine
the balanced audio signal with two 22VAC signals and a ground reference to feed the
externally connected powered speakers connected to output A, B and C. Each zone
also includes a Remote Zone Level port, which allows an external level control and
adjustment for each of the six zones.
Zone Control
Each Zone has a front panel Master Level control
(1) and a Link indicator light (2).
When the rear panel link button is pushed in the
front panel link light will illuminate indicating that
the zone has been linked with the next zone in the
Master Control Module. When linked to the next
zone the Master Level control will now control the
level of both zones and the second zone level
control will not have any effect on the level.
Zone Level Control
The front panel Master Level control will adjust the level of the zone and will also set
the maximum level of each zone. Each zone also includes a rear panel remote zone
port, which allows connection of a remote zone level control.
NOTE: The front panel Master Level control is the Zone MASTER and sets the maximum
level while the rear Remote Zone level control connected to the rear port will only allow
adjustment from a minimum setting to the maximum level set on the front panel Master
Level. This allows the Master Control Module to be placed in a location where access to
the Master Levels can be restricted and yet allows Remote Level access at a remote
location.