Motorola MSF 5000 Instruction Manual page 70

Chapter 1 Description
MSF
5000
Instruction Manual
TTRC
Audio Board
At-
LINE
1DC
+/-
JUMPERS CURRENT
+/-
OPTICAL
ISOLATORS
LINE
2
DC
+/-
--»
MSFI081
022294JNM
Figure
1-13
DC Remote Control Circuitry
Receive
Notch Filter
LINE AUDIO
from the
SSCB
enters the
TTRC
board at a nominal level of
325
mV
rms.
The notch filter output is routed through
a line shaping filter before going to the
Line
2
or
Line
4
summing
amps.
This line shaping filter is identical
to that
described
in
the transmit audio
circuitry..
In secure systems, the receive notch filter and line shaping filter should
be
bypassed.
This
is automatically accomplished
by
a
transmission gate controlled
via
the
RSS codeplug
parameters for the
TTRC
Logic
board.
Summer/line
Adjust
Notched or un-notched receive audio from the transmission gate is sent to the
summing amp for Line
2
or
Line
4 audio. These stages also sum the tones
generated
by
the
TTRC
Logic
board.
For Line
2, the output audio signal is sent
over two paths. Path
1
is directed to the
audio
gate; path 2 is routed through
a
Spectra-TAC™ equalizer
filter.
Spectra-TAC™ Equalizer Filter
This
path is activated
with
a
RSS
programmable field and when the station is
configured and programmed
as a
Spectra-TAC™
system.
Two EEPOTs equalize
the
high
and
low
end line levels compensating for phone line loss.
Line Driver and Cancellation Circuit
The Line
2
wireline line driver
uses
two operational amplifiers
to
drive
a
push-pull
arrangement.
The cancellation circuit is used in only 2-wire systems, when both incoming and
outgoing wireline audio is on Line
2.
This
circuit can be disabled
by moving
JU4205 and JU4222 to their alternate position for
a
4-wire system.
1-32
68P81092E02
3/19/94
ISOLATORS