Volume Control; Main Keypad; Lcd Module; Keypad Backlighting - Tait TM9100 Service Manual

A 3.3V regulator (U1) converts the switched 13.8V supply from the radio
Power Supply
body to 3.3V. A 1.5V regulator (U203) converts the 3.3V to 1.5V.
A power-sense module (U202) verifies the outputs of the voltage regulators
and—in the case of a fault—creates a power reset signal which is processed
by the FPGA.
The voltage level of the volume control potentiometer is converted to a

Volume Control

digital signal by an analog/digital converter (U601), processed by the FPGA
and transmitted to the radio body.
The eight keys of the main keypad (function, scroll and selection keys) are

Main Keypad

connected to the FPGA by an array of 3 columns and 3 rows. During idle
operation, the
signals (pulled high by an external resistor) are monitored for activity by the
FPGA. A key-press will generate a high-to-low transition on the associated
column
levels on the
The LCD module is connected to the control-head board via the LCD

LCD Module

connector. The LCD module display is controlled by a serial data link to the
FPGA. The backlighting and the optional heating element incorporated in
the LCD module are controlled by a data line each from the FPGA, which
switch two transistors on MOSFET Q102. A temperature signal from the
LCD module is converted to a digital signal by an analog/digital converter
(U601) and processed by the FPGA.
The function key LEDs (F1 and F4) and the red, green and amber status
Function Key LEDs
and Status LEDs
LEDs each are controlled by an FPGA signal and a transistor (Q604 to
Q608). The brightness level is controlled by two FPGA signals, resulting in
four intensity levels (off, low, medium and high).
The keypad backlighting LEDs are controlled by two FPGA signals and two
Keypad
Backlighting
transistors (Q2), resulting in four intensity levels (off, low, medium and
high). The keypad backlighting LEDs are arranged in two groups for the
main keypad and one group for the power button keypad, each group
consisting of three LEDs.
The two speaker lines (SPK+ and SPK–) are connected to the speaker
Speaker
connector (J104) which is joined to the control-head connector (J103)
through two ferrite beads (L105 and L106).
The audio signals from the microphone connector or the soldering pads of
Microphone and
Concealed
the concealed microphone are routed to a switching and pre-amplifier
Microphone
circuit. If a dynamic microphone is required, the pre-amplifier is engaged.
The switching logic is used to select either the standard microphone input
or the concealed microphone signal. The dynamic microphone must be
activated in the programming software.
The PTT signal from the microphone connector is connected to the FPGA
PTT
via a resistor (R25) and relayed to the radio as a digital command.
92 Circuit Descriptions
signals are driven low by the FPGA and the
KEY ROW
signal. This, in turn, will initiate a sequence of high output
KEY COL
signals to identify which key was pressed.
KEY ROW
KEY COL
TM9100 Service Manual
© Tait Electronics Limited August 2005