Icom IC-F5012 Service Manual page 12

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
IC21
DISC
From the IF IC
AMP
DISC
DISC
(TCSS/DTCS signals)
IC16
IC14
RXAF
HPF
ANALOG
SW
VRAF TMONI
D/A
IC18
IC16
SDEC
LPF
(2/5 TONE signals)
To the CPU (FRONT UNIT: IC1)
Q39
CDEC
LPF
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.
IC16
LPF
IC15
AF
AMP
AF
AF ON
MUTE
Q35,36,D29
FRONT UNIT
5 - 2
IC8
J4
AF
POWER
AMP
Ext. speaker jack
Int. speaker