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CIRCUIT DESCRIPTION
7.
LCD Assembly
'
The LCD assembiy consists of CPU, LCD, power
switch circuit, and tone generator.
7-1. CPU
The CPU (IC2) carrres o u t the f o l o w l n g main
operatlons:
It sends onloff data serially t o the control unit from
the AF volume control, LIPIDOWN key, system UP/
DOWN key, group UPIDOWN key, SCAlV key, and
AUX key. It receives serial data from the control unit
and displays it on the LCD.
The LCD can indicate alphanumeric characters
(13
segments, 8 d~gits), TX, BUSY, CALL, SCAN, Talk-
around, Option, AUX, TEL, and Delete.
7-2. Power switch circuit
Each time the power key
IS
pressed, a pulse
IS
sent
t o the TX-RX unlt t o turn the
transceiver
on or off.
7-3. Tone generator
The beeps and alert t o n e s are generated by
combining square wave
signals
of about 700Hz,
900Hz, and 1500Hz generated by the CPU
These
signals are output from pins 46, 47, and 48 of the CPU
(IC2). The signals are
rectified
by a CR network and fed
t o the TX-RX unit LCD assembly and the de-emphasis
circuit of IC9 (212).
Fig. 10 Tone generator circuit
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