Kenwood NX-3720HG Service Manual page 21

2.4.8 Signaling Circuit
2.4.8.1 Encode (QT/DQT/DTMF/2-tone /MSK)
Each signaling data signal of QT, DQT, DTMF, 2-tone and MSK is generated by IC404, superposed on a modulation signal and output
to VCO and PLL.
2.4.8.2 Decode (QT/DQT/DTMF/2-tone/MSK)
The audio signal and signaling data (QT, DQT, DTMF, 2-tone and MSK) are separated by IC404. Next IC404 decode the signaling
data.
2.4.9 Bluetooth/GPS Circuit (GPS model only)
The main component of the Bluetooth/GPS circuit is Bluetooth/GPS IC (IC5) on Module unit.
The clocks of Bluetooth/GPS IC require 19.2MHz for core and 32.768 kHz slow clock (X1 and X2) for UART.
Bluetooth/GPS IC communicates to the MPU/DSP (IC404) on the HCI UART. Interface of UART & Digital audio (PCM) between the
MPU/DSP (IC404) and the Bluetooth/GPS IC (IC5), have level conversion at the level conversion IC (IC6 and IC7) on Module unit.
The Bluetooth/GPS IC is powered by 1.8V and 3.3V which are supplied from 2 discrete external regulators (IC2 and IC3) on Module
unit.
IC404
UART
MPU/DSP
PCM
TX-RX unit
IC6
UART UART
Level
Conversion
IC
IC7
PCM PCM
Level
Conversion
IC
Module unit
Fig.5 Bluetooth/GPS Circuit
IC5
BPF
BT/GPS
IC
BPF
X1 X2
TCXO 32.768kHz
19.2MHz
Clock
Bluetooth
antenna
GPS
antenna
connector
CN5
(No.RA054<Rev.001>)1-21