Motorola P100 Series, Detailed Service Manual, Page: 35 / 336

Controller Theory of Operation: TX Audio Circuit 4-3
4.2 TX Audio Circuit
The TX audio circuit consists of MIC/External MIC, LPF, Audio processor IC, and TX Sub-tone
system. For UHF1 and UHF2, refer to Figure 4-2. For VHF, refer to Figure 4-3.
Figure 4-2. TX Audio Circuit (UHF1 and UHF2)
Figure 4-3. TX Audio Circuit (VHF)
VR 1
(H P F)
L imiter
Scramb l er/
D escramb l er
Sp l atter SM F
T X / RX H P F
T XA 1
-6 to +4. 5 d B/
1 . 5 d B
-9.6 to +3d B/
0. 2 d B
Aud io Processor I C (AK 2 347)
Tone IN
(f rom CPU )
VR 5
S u b a ud io
Programmab l e
L P F
pin 4
pin1 7
pin 8
U1 0 2
-6 to +6d B/
0. 5 d B
F c =300Hz
VR 2
Pre -
E mp h asis
Com -
pressor
D T A 1
pin1 9
To V C O &
V CTC XO
2 O r d er L P F
(F c =300Hz)
U5 0 2 -A
Mo d.Adj,
6 O r d er L P F
(F c =3KHz)
U5 0 1 -A, B
U5 08
T X AF A mp .
U5 0 2 - C
4 O r d er L P F
(F c =4KHz)
U5 0 1 - C ,D
Mic
(Aud io IN)
F c = 2 . 55 KHz /
3KHz
VR 1
(H P F)
L imiter
Scramb l er/
D escramb l er
Sp l atter SM F
T X / RX H P F
T XA 1
-6 to +4. 5 d B/
1 . 5 d B
-9.6 to +3d B/
0. 2 d B
Aud io Processor I C (AK 2 347)
Tone IN
(f rom CPU )
VR 5
S u b a ud io
Programmab l e
L P F
pin 4
pin1 7
pin 8
U1 0 2
-6 to +6d B/
0. 5 d B
F c =300Hz
VR 2
Pre -
E mp h asis
Com -
pressor
D T A 1
pin1 9
To V C O &
V CTC XO
2 O r d er L P F
(F c =300Hz)
U5 0 2 -A
6 O r d er L P F
(F c =3KHz)
U5 0 1 -A, B
Mo d.Adj,
U5 08
T X AF A mp .
U5 0 2 - C
4 O r d er L P F
(F c =4KHz)
U5 0 1 - C ,D
Mic
(Aud io IN)
F c = 2 . 55 KHz /
3KHz