TB9100/P25 CG/P25 TAG Installation and Operation Manual Technical Description 133
© Tait Limited March 2014
Figure 8.7 shows the configuration of the main circuit blocks, and the main
inputs and outputs for power, audio and control signals.
Audio Circuitry The volume of the speaker is controlled by the volume control knob. In
addition, the control panel performs gain control so that, with an input of
167mV pp, the power output into a 16Ω speaker is ≥0.5W at the maximum
position of the knob, and 0W at the minimum position of the knob. Speaker
audio is from the currently selected reciter only. An LED indicates when the
speaker is on.
The control panel is designed to work with an electret microphone with an
input range of 80dBSPL to 115dBSPL.
Signal Switching Speaker audio and power for the control panel are common signals for all
reciters in the subrack. The remaining signals (microphone audio, I2C mess-
ages, and fan power) are switched so that only one reciter is connected to
the control panel at a time. This switching takes place on the subrack inter-
connect board and is controlled by the channel button on the control panel.
Figure 8.8 shows signal paths and switching operations performed between
the control panel and subrack interconnect board.
Figure 8.7 Control panel high-level diagram
IC
Translation
2
Microphone
Pre-emphasis
& Gain Control
Speaker
Volume &
Gain Control
Monitor LEDs
& Switches
Channel LEDs
Control
Panel Type
Microphone
Connector
Speaker
Fan Rotation
Power
Supply
Channel LED
Control &
Decoding
Microphone Audio
Switched
Signals
Fixed
Signal Lines
Speaker
Enable
I C Bus
2
V , GNDIN
Channel LED Signalling
Reciter Counter
PTT
to subrack
interconnect board
via 26-way D-range
Speaker Audio
Channel Select
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