5 - 2
LPF
IC16
LPF
IC16
LPF
Q39
HPF
IC16
AF
AMP
IC15
AF
POWER
AMP
IC8
AM
P
IC21
AF
MUTE
Q35,36,D29
Int. speaker
Ext. speaker jack
J4
ANALOG
SW
SDEC
To the CPU (FRONT UNIT: IC1)
CDEC
IC14
D/A
IC18
(2/5 TONE signals)
(TCSS/DTCS signals)
FRONT UNIT
AF ON
DISC
From the IF IC
DISC
DISC
VRAF
TMONI
RXAF
AF CIRCUITS (MAIN-A UNIT)
The demodulated AF signal from the IF demodulator IC (IC1)
is amplified by the AMP (IC21), filtered by the HPF (IC16),
and then passed through the AF line SW (IC14) and LPF
(IC16). The filtered AF signal is adjusted in level (=loudness)
by the D/A converter (IC18), and applied to the AF AMP
(IC15) through the AF line SW (IC14).
The amplified AF signal is applied to the AF power AMP (IC8)
and power-amplified to obtain AF output level.
The power-amplified AF signal is output from the external
speaker jack (J4) on the rear panel, or applied to the
internal speaker on the FRONT UNIT, through the external
speaker jack (J4).
• RX AF CIRCUITS
SIGNALING (DECODING) (MAIN-A UNIT)
Demodulated signal from the pin 9 of the IF demodulator
IC (IC1) is passed through the LPF to extract tone signals
contained in the demodulated signal.
2/5 tone signal is extracted by the LPF (IC16). CTCSS/
DTCS signals are extracted by the LPF (Q39).
These extracted tone signal is applied to the CPU (FRONT
UNIT: IC1) for decoding.
