il!itellabs
technical manual
76-844001C
rev A
practice section
844001C
©Tellabs, Inc., 1August 1986
all rights reserved, printed in USA
4001C
Prescription Line Amplifier
1.
general
description
1.01 The 4001CPrescription
Line
Amplifier mod-
ule (figure
1)
provides active prescription level con-
trol, active prescription
amplitude
equalization,
and
impedance
matching
for
the transmit
and
receive
channels
of
a
4wire
voice-frequency
transmission
facility. The
4001C
also
contains
two
independent
sealing-current sources,
one
on the
facility
side
and
the
other
on
the
terminal
side
of
the
module.
Note:
Because
the
4001C
has
identical
equalizers
in
both
channels,
identical
impedance-matching
capabilities
at
all
four
ports,
and
identical
sealing-
current
sources
on
the
facility
and
terminal
sides, it
can
be
used
either
at
an
intermediate
point
or
near
an
end
point
of
a
4wire
facility.
Although
the
terms
"facility
side"
and
"terminal
side"
do
not
strictly
apply
in
intermediate
applications, these terms will,
for
convenience,
be
used
throughout
this
practice
as follows:
Facility
side
will
refer
to
the
receive
input,
transmit-output
side
of
the
4001C,
and
ter-
minal
side
will
refer
to the transmit-input, receive-
output
side
as
shown
on
the
block
diagram
in
section
5
of
this practice.
1.02 This practice
section
is reissued
to
cover
the
Issue 4version
of
the
4001C
module
(Tellabs
part
number
844001
C).
The
Issue 4
module
is identical
to its Issue 3
predecessor
except
for
the
addition
of
afront-panel power-on
indicator
LED.
1.03 The 4001C's
transmit
and
receive amplifiers
can be
independently
prescription-set
to
provide
from 0to
24dB
of
loss
or
0to
24dB
of gain in
their
respective channels. For
each
channel, gain
or
loss
is
selected
via afront-panel slide switch. The de-
sired
amount
of
gain
or
loss is
then
introduced
into
each channel in precise
0.1
dB
increments
via a
front-panel DIP switch. The maximum
output
level
of
each channel is
+10dBm,
with
distortion
at max-
imum
output
less than 1percent.
1.04 All
four
ports
of
the
4001C
module
can be
switch-optioned
for
balanced 1200, 600,
or
150-
ohm
terminating
impedance. The
impedance
of
the
two
facility-side
ports
is
selected
independently
from
that
of
the
two
terminal-side ports. The trans-
formers
at
all
four
ports
of the
module
are center-
tapped
to
derive balanced simplex leads.
•
•
contents
section
1
general
description
section
2
application
section
3
installation
section
4
circuit
description
section
5
block
diagram
section
6
specifications
section
7
testing
and
troubleshooting
page
1
page
2
page
4
page
8
page
10
page
9
page
11
figure
1.
400
1C
Prescription Line
Amplifier
1.05
In
addition to active prescription level-control
circuitry, the 4001Ccontains active prescription
slope-type
amplitude-equalization
circuitry
in both
channels. The
transmit
and receive equalizers are
identical,
each
providing from 0
to
7.5dB of gain
at
2804Hz
(re 1004Hz). Equalization is
introduced
into
each
channel
independently, in 0.5dB increments,
via DIP
switches
on
the
module's
front panel.
1.06 The
4001C
can be
optioned
to
provide
25mA
of internally
generated
sealing current
to
metallic facilities on the
facility
and terminal sides
of
the
module,
to
accept
externally
generated
seal-
ing
current
from the
far
ends
of the facilities on both
sides
of
the
module,
to
derive normal simplex leads
on
both
sides of the module,
or
to provide bypassed
(straight-through) simplex-lead signaling via apath
separate from
the
transmit and receive transmission
paths. Each of
the
4001C's
two
internal sealing-
current
sources
has a"ZAP" feature by which a
greater
amount
of sealing
current
is provided
for
a
few
seconds
when
power
is initially applied to the
module.
1.07 The
front
panel of the
4001C
is designed so
that
all level and equalization
adjustments
can be
made
while
the
module
is
mounted
in place. Six
front-panel
bantam-type
test
jacks
facilitate align-
ment
and
maintenance. Both bridging and opening
jacks
are provided at
the
facility-side ports; opening
jacks
alone are provided
at
the terminal side ports.
Front-panel
seal
curr
1and
seal
curr
2LED's light
when
the
module's
internal facility-side and ter-
minal-side sealing-current options, respectively, are
activated and sealing
current
is flowing. Also
located on the front-panel is a
pwr
on LED that
lights when
power
is applied
to
the
module.
page
1
