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(superscript: Then, the 1st IF signal (10.555MHz) is mixed with 2nd local
frequency of 10.100MHz to produce the 2nd IF of 455kHz at IC3, and also
AF output is obtained by IC3. The demodulated signal by IC3 contains a
security code, and the code is fed to the CPU.)
(superscript: TX Circuit:)
(superscript: TX VCO signal is generated at the PLL circuit and the TX
VCO (IC202 2/2). Meanwhile, voice signal from Telephone Network through
the Hybrid Transformer (T1) modulates the TX VCO signal at IC202. This
modulated signal is the TX RF frequencies as listed above. Then, the TX
RF signal is amplified by RF AMP (Q206/Q207) and fed into the antenna
through a band pass filter (FT201).)
(superscript: 3) Dialing Signal)
(superscript: Dial pulse code sent from the handset is demodulated by IC3
as mentioned above, and is fed into the CPU to control RL1.)
(superscript: 4) Telephone Interface Circuit)
(superscript: Outgoing voice signal to telephone network is amplified by
IC1 and Q3. This signal is delivered to the telephone interface circuit
through the Hybrid Transformer (T1).)
(superscript: Incoming voice signal also goes through T1, then it is
amplified by Q4 and IC1 2/2 to a proper level for frequency modulation,
then it is fed to the TX circuit. To protect the TX/RX circuits from a
metallic surge, the surge absorbing capacitor (C20) is provided at the
secondary circuit of the Hybrid Transformer (T1).)
(superscript: 5) Bell Signal)
(superscript: An alerting signal (Bell signal) is detected by means of a
Photo Coupler (IC4) which has a sufficiently high impedance.)
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