Icom ID-1 Service Manual page 9

signals are applied to the CPU (IC50) via the FPGA IC
(IC200).
• DV MODE (VOICE OPERATION)
The digital audio signals from the CPU (IC50) are applied
to the AMBE CODEC IC (IC2) for code expansion, and are
then applied to the linear CODEC IC (IC1). The digital audio
signals are converted into analog audio signals at the D/A
converter section and then output from pin 34 (IC1)
The analog audio signals are applied to the mode switch
(MAIN unit; IC1411, pins 1, 7) via the J101 (pin 30) as "DAF"
signal.
• DD MODE/DV MODE (LOW SPEED DATA OPERATION)
While operating in DD mode, the output signals from
the CPU (IC50) are applied to the connected PC via the
Ethernet controller (IC104).
While operating in DV mode (low speed data operation), the
output signals from the CPU (IC50) are applied to the con-
nected PC via the USB controller (IC550).
4-1-7 AF AMPLIFIER CIRCUIT (MAIN UNIT)
The AF amplifier circuit amplifies the demodulated AF sig-
nals to a level needed to drive a speaker.
• DV MODE
The AF signals from the LOGIC-1 unit are applied to the
mode switch (IC1411, pins 1, 7) and then amplified at the
buffer amplifier (IC1460, pins 1, 3). The buffer amplified
signals are applied to the filter switch (IC1462, pins 1, 6)
to select the appropriate AF filters for DV mode and then
passed through the low-pass (IC1461, pins 8, 10) and high-
pass (IC1461, pins 12, 14) filters. The filtered signals are
passed through the filter switch (IC1463, pins 1, 6) and are
then applied to the volume controller (IC1550, pins 2, 9).
• FM MODE
The AF signals from the demodulator IC (IC191, pin 9) are
applied to the mode switch (IC1411, pins 1, 6) and then
applied to the buffer amplifier (IC1460, pins, 1, 3). The buf-
fer amplified signals are applied to the filter switch (IC1462,
pins, 1, 7) to select the appropriate AF filters for FM mode
and then passed through the low-pass (IC1460, pins 6, 7,
8, 9) and high-pass (IC1460, pins 13, 14) filters. The filtered
signals are passed through the filter switch (IC1463, pins 1, 7)
and are then applied to the volume controller (IC1550, pins 2,
9).
The switched AF signals from the filter switch (IC1463, pin
1) are applied to the volume controller (IC1550, pins 2, 9).
The level adjusted AF signals (IC1550, pin 9) are applied to
the AF power amplifier (IC1551, pins 1, 4) via the AF mute
switch (Q1550).
The AF mute switch is mute the AF signals while digital
squelch, call sign squelch, noise squelch, tone squelch are
closed, the audio level is set to minimum position or trans-
mitting.
The power amplified AF signals from the AF power amplifier
(IC1551, pin 4) are applied to the speaker that is connected
to [SP] jack (J1550).
4-1-8 SQUELCH CIRCUITS (MAIN UNIT)
• DIGITAL CODE/CALL SIGN SQUELCH (DV MODE ONLY)
The digital code/call sign squelch circuit detects matched
digital code/call sign and opens the squelch only when
receiving a signal containing a matching digital code/call
sign. When digital code/call sign squelch is in use, and a sig-
nal with a unmatched digital code/call sign is received, the
digital code/call sign squelch circuit mutes the AF signals.
The detected digital audio signals from IC191 (pin 9) are
applied to the CPU (LOGIC-1 unit; IC50) via the mode
switch (IC342, pins 1, 7), GMSK MODEM IC (LOGIC-1 unit;
IC150) and FPGA IC (LOGIC-1 unit; IC200). Then the CPU
analyzes the digital code/call sign and output the AF mute
signal as "RMUT" from the pin 102 to the filter switch (IC1463,
pin 2) via the mute switch (LOGIC-1 unit; Q155).
• NOISE SQUELCH (FM MODE ONLY)
The noise squelch circuit cuts out AF signals when no RF
signals are received. By detecting noise components in
the AF signals, the squelch circuit switches the filter switch
(IC1463).
Portion of the AF signals from the demodulator IC (IC191,
pin 9) are applied to the active filter section in the demodu-
lator IC (IC191, pin 8). The active filter section filters and
amplifies noise components only. The amplified noise signals
are converted into the pulse-type signals at the noise detec-
tor section. The detected signals output from pin 14 (IC191).
The detected signals from the demodulator IC (IC191,
pin 14) are amplified at the noise amplifiers (Q192, Q193)
and then applied to the noise detector (D195). The detected
signals are applied to the CPU (LOGIC-1 unit; IC50, pin 32)
as "NOIS" signals. Then the CPU analyzes the noise condi-
tion and outputs the AF mute signal as "RMUT" from the pin
102 to the filter switch (IC1463, pin 2) via the mute switch
(LOGIC-1 unit; Q155).
• TONE SQUELCH (FM MODE ONLY)
The tone squelch circuit detects tone signals and opens the
squelch only when receiving a signal containing a matching
subaudible tone (CTCSS). When tone squelch is in use, and
a signal with a unmatched or no subaudible tone is received,
the tone squelch circuit mutes the AF signals even when
noise squelch is open.
A portion of "DEAF" signals from the buffer amplifier (IC1460,
pin 1) are applied to the low-pass filters (IC1461, pins 1, 2,
5, 7) to remove AF (voice) signals. The filtered signals are
applied to the CTCSS decoder in the CPU (LOGIC-1 unit,
IC50, pin 33) as "TONI" signals. Then the CPU analyzes
the decoded tone signals and output the AF mute signal as
"RMUT" from the pin 102 to the filter switch (IC1463, pin 2)
via the mute switch (LOGIC-1 unit; Q155).
4-1-9 S-METER CIRCUITS (MAIN UNIT)
Some of the amplified IF signal is applied to the S-meter
detector section in the demodulator IC (IC191) to be con-
verted into DC voltage. The output signal from the demodu-
lator IC (IC191, pin 12) is applied to the mode switch (IC341,
pins 10, 11) and then applied to the CPU (LOGIC-1 unit;
IC50). The CPU then outputs S-meter control signal to the
RC-24 or connected PC via the USB controller (LOGIC-1
unit; IC550).
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