24 Circuit Description TB8100 Installation and Operation Manual
© Tait Electronics Limited June 2005
saving feature to operate. Refer to “Power Saving” on page 57 for more
information.
Auxiliary Power
Supply
This optional power supply board is mounted on the DC module. The
input power is provided from the PA output of the HVDC circuitry on the
AC converter board. It provides a high quality 13.65VDC, 27.3VDC or
54.6VDC output (depending on the model) to power external accessory
equipment, or can be used to trickle-charge batteries. It can be configured
using the Service Kit software to operate whenever mains voltage is
available, or whenever the PA output is available.
Microprocessor The microprocessor on the HVDC control card monitors and controls the
operation of the PMU. There are no manual adjustments in the PMU
because all the calibration voltages and currents required to control and
protect the PMU are monitored by the microprocessor. The software also
automatically detects the PMU configuration and controls the PMU
accordingly.
If any of the monitored conditions exceeds its normal range of values, the
microprocessor will generate an alarm and take appropriate action,
depending on the configuration of the PMU.
The alarms and diagnostic functions are accessed through I
2
C bus messages
on the system control bus via the reciter, control panel and Service Kit
software.
The operation of the cooling fan mounted on the front panel is determined
by the temperature limits set in the PMU software.
Important In base station systems which use a PMU, the PMU must
be connected to the system control bus at all times. The
I
2
C current source is located in the PMU, and if the PMU
is disconnected, the state of much of the bus will be unde-
fined. This may cause corrupted data to be present on the
bus when the reciter reads the states of the switches on the
control panel. This in turn may result in random actuations
of microphone PTT, carrier, or speaker key, causing the
BSS to transmit or the speaker to be actuated incorrectly.
2.4 Control Panel
The control panel is designed to be the link between the user and the
TB8100 BSS. The circuitry for the operation of the control panel is located
on a board mounted behind its front face. All communication between the
BSS and the control panel is via the system control bus. Figure 2.5 on
page 25 shows the configuration of the main circuit blocks, and the main
inputs and outputs for power, audio and control signals for the standard,
dual base station, and Power Save control panels.
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