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HARRIS
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WARNING: Disconnect and lockout AC primary power prior to servicing
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Section 5
5
Control System
Theory
5.1 Control System Overall Description
The control system for the Harris Platinum-i series of VHF TV transmitters consists of
a Control Cabinet that contains a controller board, front panel interface, and the GUI
monitoring system. The main controller printed wiring board is mounted on the
underside of the Input/Output panel located at the top of the control cabinet..
Each PA Cabinet has a slave controller, communicating with the control cabinet over a
parallel bus and command lines. The slave controller has monitoring, protection and
control functions.
NOTE:
Each logic signal has an active and inactive state and a unique name within the
system. To differentiate between active high or active low logic states on the
schematics, a forward slash (/) is placed in front of an active LOW signal name
such as /RF_MUTE. This means that if this logic line is pulled low, the
transmitter RF will be muted. By the same logic, the signal RF_MUTE_LED (an
active high signal with no forward slash) will turn on the RF mute LED when it
goes high. In some cases, a logic signal may act as a toggle with both states
active, as with the signal /ON_OFF, where LOW = ON and a HIGH = OFF. If
this signal is inverted it would be ON_/OFF.
5.2 Transmitter Control System
The Platinum-i transmitters utilize a very advanced but simple to use control system. It
is a microprocessor, serial communication based software control system but uses
backup Life Support logic circuitry and hard wired control lines, allowing the
transmitter to be on the air even if the main control system fails.