Power Supply Circuit; Signaling Circuit; Encode; Decode - Kenwood NX-1200 Series Service Manual

2.3.7 Power Supply Circuit

The battery voltage (+B) is provided from battery terminal. The battery voltage passes through the 3.15A fuse (F400), and goes to
RF Drive and final amplifier, DC/DC converter (IC407), AF amplifier (IC300 through the 1.0A fuse (F300)), and INT DET IC (IC406).
IC406 monitors battery voltage. If the battery voltage is enough higher than 5.6V, IC406 outputs "High".
When the Power SW is turned on, SB becomes "High" (battery voltage). DC/DC (IC408) operates if both SB and IC406 output are
"High". IC407 (38M) outputs 3.8V, and IC404 (32M) outputs 3.2V. IC408 (32MD) outputs 3.2V. IC203 (32B) outputs 3.2V. Reset IC
(IC405) watches IC408 (32MD) output voltage. If the 32MD output voltage is enough higher than 2.8V, Reset IC (IC405) outputs
"High". As a result, MPU/DSP (IC501) operates.
SBC signal becomes "High" after MPU/DSP (IC501) operates, and IC400 (50M), IC401 (50C), IC403 (32C), and IC1 (32MS) are
turned on.
When 50VC signal becomes "High", IC402 (50V) operates. When 5TC signal becomes "High", Q400 (50T) is turned on. Q400 (50T)
is turned on in transmit mode. Switches are controlled by MPU/DSP (IC501).
When the Power SW is turned off, /SB_DET signal becomes "High". After detecting /SB_DET signal, MPU/DSP (IC501) changes SBC
signal to "Low".
38M is fed to IC3 (200C). IC3 (200C) is the DC/DC boost converter. IC3, D1, C34 consist of a voltage quadrupler.
The 200C circuit then outputs approximately +20VDC.

2.3.8 Signaling Circuit

2.3.8.1 Encode (QT/DQT/DTMF/2-tone/MSK)
Each signaling data signal of QT, DQT, DTMF, 2-tone and MSK is generated by the MPU/DSP (IC501), superposed on a modulation
signal and output to VCO and PLL.
2.3.8.2 Decode (QT/DQT/DTMF/2-tone/MSK)
The audio signal and signaling data (QT, DQT, DTMF, 2-tone and MSK) are separated by the MPU/DSP (IC501). Next the MPU/DSP
(IC501) decode the signaling data.
F400
BATT
GND
Power SW
SB
D401 INT
DC SW
SBC/PWR
D402
IC407
DC/DC
SBC/PWR
/SB_DET
5TC
32CC
IC501
50VC
MPU/DSP
SBC
32MC
Fig.5 Power Supply Circuit
IC400
AVR
Q400
SBC
DC SW
5TC
IC402
AVR
IC401 50VC
AVR
32CC
IC406
INT DET
38M
IC404
AVR
IC405
SBC/PWR
RESET
IC408
DC/DC
SBC/PWR
IC1
AVR
32MSC
IC203
AVR
IC403
AVR
32CC
IC3
DC/DC
+B
50M
50T
50V
50C
INT
32M
RESET
32MD
32MS
32B
32C
200C
(No.RA077<Rev.001>)1-11