15.5
VOICE FILTER
R1
TP2
U1
C6
C1
R2
R4
4
U2
U3
U5
R19
R25
R33
R39
R43
TP1
TP3
C4
C5
C7
C9
C8
C3
C1
1
C1
0
C1
2
C1
7
C1
6
P1
C2
2
C2
3
C2
4
C29
C25
C2
6
C3
1
C30
C19
C3
2
C27
C2
8
C3
5
C34
C1
3
C1
4
C15
C1
8
C21
C3
3
R3
R4
R7
R8
R9
R1
0
R1
1
R1
2
R13
R14
R15
R16
R18
R17
R2
1
R2
0
R2
2
R2
3
R2
4
R2
7
R2
8
R2
6
R34
R30
R29
R31
R32
R3
5
R3
8
R3
7
R3
6
R4
1
R4
0
R4
2
U4
P2
C20
C3
6
C3
7
106583 REV B
1999 RFL ELECTRONICS INC
FILTER
97 VOICE
1
1
Figure 15-6. RFL 9785 Voice Filter
15.5.1
DESCRIPTION
The Voice Filter (Figure 15-6) plugs onto the Receiver Detector module (Section 12) only when the
RFL 9785 has the voice option installed.
The voice filter is a 6Khz wide bandpass filter centered at 24Khz. It accepts the signal output from the
Receiver Downshifter module (Section 11) and passes the portion of the band containing voice, to the
Voice Module (Section 15).
The signal presented by the Receiver Downshifter module enters the Receiver Detector module on
edge pin connector A14, which can be measured at test point TP2 of the Receiver Detector module.
This is passed through connector J1-1/P1-1 to the input of the voice filter. The output of the voice filter
is passed through connector J2-1/P2-1 to the main circuit board, and can be measured at test point TP3
on the Receiver Detector module.
Resistors R10, R11 and R12 which are connected in series, form a voltage divider for the output of the
voice filter. The voltage divider has taps which are routed through an analog switch. The analog switch
controls the voice output which can be voice high, voice low, or muted. The 24Khz voice output exits
the Receiver Detector board on connector pin C14. It then enters the voice module on connector pin
A14, where it is demodulated and further processed.
NOTE
The plug-on voice filter is only used on the RFL 9785 when the voice option is used. This
filter contains five potentiometers. Only one of these potentiometers (R43) can be adjusted
in the field, using the instructions given in Section 4 of this manual. Any attempt to adjust
any other potentiometers on the voice filter may result in voice degradation.
RFL 9785
RFL Electronics Inc.
April 25, 2005
15-11
(973) 334-3100