Bell System CENTRA-LINE 612A Maintenance Manual

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BELL SYSTEM PRACTICE
SW BELL TEL. CO.
SECTION 662-495-901SW
Issue A, November, 1975
REMOTE TEST SYSTEM
CENTRA-LINE 612A
MAINTENANCE
1. GENERAL
1.01 This Section contains maintenance inst-
ructions for the CENTRA-LINE 612A
Remote Testing System.
1.02 This Section includes a functional des-
cription of the system, troubleshooting
procedures, periodic checks and adjustment
procedures, information on replacement and
repair parts, and system specifications.
1.03 It is recommended that maintenance
personnel become familiar with Section
662-495-900SW, Operation and Test Procedures,
before attempting to perform maintenance on
this system.
2. FUNCTIONAL DESCRIPTION
2.01 A description of every card's contri-
bution to the operation of the system
is provided in the following paragraphs.
Supplementing this description is a photo-
graph of the master station and one of the
remote station, and also a block diagram of
each station. The photographs point out the
physical location of every card, while the
block diagrams show their electrical rel-
ationships.
2.02
MASTER STATION -Figure 1A is a rear
view of the master station with its
cover off, exposing the arrangement of the
cards within. A retaining bar, which extends
across the front of the cards and is designed
to hold them in place, has also been removed
to reveal the cards in their entirety. Fig-
ure 18 is a front view of the master station
showing the functional grouping of the con-
sole's controls. Figure 2 is the correspond-
ing block diagram of the master station, and
the basis of the following description.
2.03 CONSOLE KEYBOARDS- Functionally, the
console control panels are separated
into four keyboard groups, each of which has
a number of pushbuttons. All control oper-
ation and meter function pushbuttons are
arranged in a logic OR configuration. Thus,
when any of them is pressed, it connects a
ground potential to one of two,.matrices,
meter function or control ops, initiating a
unique code in the scanner. To allow the use
of binary coding·, mechanical interlocking is
employed within each keyboard group. (The
details of the coding in terms of d-e logic
levels are described in paragraph 3.) The
DIAL TONE, LINE REVerse, and auxiliary
CONTrol {1 through 7) pushbuttons initiate
independent functions. The IN-DIAL push-
button, however, must be· used in conjunction
with other pushbuttons (see paragraph 2.05)
in order to initiate the in-dial function.
2.04 METER FUNCTION MATRIX- The meter func-
tion matrix is associated with the
meter function keyboard and with control
pushbuttons 1 through 7. Operation of any
pushbutton in the meter function group causes
the matrix to produce, in parallel form, a
binary~coded d-e input at the scanner. Logic
gating circuits in the matrix develop the
proper code for each input function.
2.05 CONTROL OPS MATRIX- This matrix re-
ceives its input from the control oper-
ations keyboard and from the dial-tone, line-
reverse and in-dial functions. Like the
meter function matrix, it provides, in par-
allel form, a binary-coded d-e output to the
scanner whenever any of its associated key-
board pushbuttons is operated. When this
occurs, the matrix's electronic interlocking
circuits inhibit the keyboard associated
with the meter function matrix. Operation
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