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it is converted to10.7 MHz and 455 KHz Intermediate by RF IC. The demodulated audio signal is
output from RF IC
(DET OUT) and passed through "Expander" process to reduce noise, then voice signal is led to
LINE AMP. The signal is
passed through TELEPHONE INTERFACE and Tel-line.
RX data (from Handset):
The data signal from handset (ex: Talk, ACK, COM) is also included in 49 MHz band same as the
voice data. After second if
filter, the data signal is made square shape by data limiting AMP of the RF IC. RX data is output
to CPU (RX Data).
16.6.3. RF signal operation/control and PLL operation (RF UNIT)
Base unit radio frequency signal received by antenna passes through duplexer (DPX1).
RF signal is amplified by RF AMP. RF signal received from RF IC is mixed with RX local
frequency at Mixer to generate
10.7 MHz wide band IF. The reference frequency is generated by X1 10.245 MHz crystal. VC1 is
the reference frequency
for adjustment. The 10.7 MHz is mixed with reference and 455KHz narrow band IF is generated.
The demodulation audio signal
is adjusted to the maximum at T1. RF IC is controlled by CPU (RF_STB, DATA, CLK). The RX
local frequency is generated
by RXVCO.
16.7. Signal Route
Each signal route is as follows.
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