NX-900
22
8. Signaling Circuit
8-1. Encode (QT/DQT/DTMF/MSK)
Each signaling data signal of QT, DQT, DTMF and MSK
is generated by the DSP circuit, is superimposed onto the
modulation signal, and is output from the DSP (IC717) and
ASIC (IC510). The modulation balance of the QT/DQT signal
is adjusted by the D/A converter (IC719) and the resulting
signal is routed to the modulation input of the VCO and PLL
IC (IC3). Each deviation of the TX QT, DQT, DTMF and MSK
signal is adjusted by changing the output level of IC717 and
the resulting signal is routed to the VCO and PLL IC (IC3).
The RX DTMF tone is routed to the receive audio signal sys-
tem, and is output from the speaker.
8-2. Decode (QT/DQT/DTMF/MSK)
The audio signal is removed from the FM detection
signal sent to the DSP circuit and the resulting signal is de-
coded.
9. Compander Circuit
The term “compander” means compressor and expand-
er. The compander reduces noise by utilizing a compressor
and an expander. The NX-900 contains a DSP (IC717) to per-
form this operation. The NX-900 compander can be turned
on or off using the FPU.
CIRCUIT DESCRIPTION
IC403
8V AVR
Q407
DC SW
Q408
DC SW
IC404
5V AVR
Q409
DC SW
TXC
RXC
Q404
DC SW
SBC_2
SBC_2
SBC
/BINT
80T
80C
SB
80R
50C
50R
IC406
3.3V AVR
33C
IC407
3.3V AVR
33GPS
F401
CN401
DCin
(13.6V)
GND
IC506
RESET
/BINT
/RST
Q405
DC SW
SCTAM1
Q411
DC SW
RXC
/RST
33BU
CN405
Backup Battery
IC402
3.3V AVR
IC405
DC/DC
50M
+B
33M
IC408
3.3V AVR
33A
IC409
1.5V AVR
D408
15M
33A_2
Q412
DC SW
Q416
DC SW
50MC
33M
SBC_2
IC401
Detect
SBC_2
/IGN
D401
Q401
Protect
Q403
CN402
CN403
1
2
Fig. 8
Summary of Contents for NEXEDGE NX-900
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