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4-4 ATIS AND DSC CIRCUITS
4-4-1 ATIS ENCODE CIRCUIT ([HOL], [FRG] ONLY)
(LOGIC BOARD AND MAIN UNIT)
The FSK signal of ATIS created at CPU (IC1) is passed
through the ladder type D/A convertor (R55–R73) to convert
into the analog signal. The analog signal is applied to the
buffer amplifier (Q8), and then applied to the mixer circuit
(MAIN unit; IC10A, pin 2) to mix with signals from the micro-
phone. The signal passes through the low-pass filter (MAIN
unit; IC10B, pins 5, 7) and is then applied to the VCO circuit
as modulation signal.
4-4-2 DSC ENCODE CIRCUIT (MAIN UNIT)
The DSC signal created at the optinal DSC controller (DS-
100) is applied to the T1 via the J7, and then as floating sys-
tem output. The signal is applied to the buffer amplifier
(Q29), and then passes through the 6 dB/oct pre-emphasis
circuit (C282, C233, R203, R207). The signal is applied to
the mixer circuit (IC10A, pin 2) to mix with signals from the
microphone. The signal passes through the low-pass filter
(IC10B, pins 5, 7) and is then applied to the VCO circuit as
modulation signal.
4-5 LOGIC CIRCUITS (LOGIC BOARD)
• CPU
IC1 is an 8 bit signal chip micro-computer and contains LCD
driver, serial I/O, timer, A/D converter, programmable I/O,
ROM and RAM.
• SYSTEM CLOCK CIRCUIT
X1 is a ceramic oscillator and oscillate 9.8304 MHz system
clock for the CPU (IC1).
• RESET CIRCUIT
IC6 is a reset IC. When turn power ON, IC6 outputs a reset
signal ("LOW" pulse) to the CPU (IC1, pin 15) via the "RES"
line.
• LOW BATTERY DETECTOR
VCC voltage is divided by R74, R75 and is applied to the low
battery detector section in the CPU (IC1, pin 91) via the
"LBAT" line.
• DIMMER CIRCUIT
CPU (IC1), Q2, Q3 and Q4 are dimmer circuit and control
the 4 steps the LCD backlight (DS3–DS8).
-
4-6 POWER SUPPLY CIRCUITS
VOLTAGE LINES
LINE
The voltage from the connected DC power sup-
HV
ply.
Same voltage as the HV line which is passed
HVS
through the [PWR] switch (VR-A board; R1).
Same voltage as the HVS line. The voltage is
VCC
applied to the optional DSC controller (DS-100).
Common 5 V converted from the VCC line at the
5V
5V regulator circuit (MAIN unit; IC8).
Transmit 5 V controlled by the T5 control circuit
(MAIN unit; Q24, Q25) using the "SEND" signal
T5
from CPU (LOGIC board; IC1). The controlled
voltage is applied to the transmitter circuit.
Receive 5 V controlled by the R5 control circuit
(MAIN unit; Q22, Q23) using the "RCV" circuit
R5
from CPU (LOGIC board; IC1). The controlled
voltage is applied to the receiver circuit.
4 - 4
DESCRIPTION
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