Bell 518-215-407 Service Manual

BELLSYSTEMPRACTICES SECTION518-215-407
AT&TCo Standard Issue 2, June 1981

SERVICE

550- AND 551-TYPE

1A2 KEY TELEPHONE SYSTEM

KEY SERVICE UNITS

1. GENERAL munications Commission (FCC) Registration

1.01 This section provides identification, installa- interface. Information on approved interfaces is con-

tion, connection, and maintenance informa- tained in Section 461-604-105, entitled Connecting

tion for the 550- and 551-type key service units Blocks, 66M3-50R--Identification, Installation, and
(KSUs). The information pertaining to the 550A, Maintenance.

551A, 550B, and 551B KSUs was formerly contained
in Sections 518-255-101 and 518-255-401. These units 1.05 SAfter January 1, 1980, a 415B KTU must be

have been rated manufacture discontinued (MD)and used when furnishing the automatic, dc sig-
replaced by the 550C and 551C KSUs. Information naling, private line feature in these units.Q

required for maintenance of existing installations of
the MD-rated KSUs has been retained in this section. 2. IDENTIFICATION

Program must be routed through a standard network

1.02 This section is reissued to: 2.01 Purpose: A 550- or 551-type KSU provides a

• Add information on the 415B key telephone (KTS) package arranged to mount four of the follow-
unit (KTU) ing KTUs:

• Change power supply to 28D2 400-type (CO or PBX Line Circuit)

• Provide information on new KS-22453 power Note: The 400H KTU is AT&TCo Standard;
cord tag the 400G, 400D, and earlier KTUs are rated MD.

• Change information on grounding require- 401-type (Manual Intercom Line Circuit)
ments.

1.03 This issue of the section is based on the follow- Line Circuit)

ing drawings:

SD-69477-01, Issue 8A

CD-69477-01, Issue 4B

If this section is to be used with equipment or appa-
ratus reflecting later issues of the drawings, refer- 2.03 Ordering Guide

ence should be made to the SD and the CD to

determine the extent of the changes and the manner (a) Basic Units (Fig. 1):
in which the section may be affected.

1.04 Incoming central office (CO) lines to be in- where suitable external source of required

stalled in compliance with the Federal Com- talk and signal voltages is available)

Not for use or disclosure outside the

Bell System except under written agreement

NOTtCE

factory-wired 1A2 key telephone system

415-type (Automatic, DC Signaling, Private

467A (Low-Voltage Monitor Circuit).

2.02 Application

• 1A2 KTS installations.

• Unit, Service, Key--550C (for installations

Printed in U.S.A. Page 1

SECTION518-215-407

• Unit, Service, Key--551C (built-in power • Cord, Power, 834167660, 2 feet*

unit).

(b) Replaceable Components:

• Interrupter, KS-19175, List 1--furnished
with 550- and 551-type KSU (requires 10-volt • Cord, Power, 824013288, 4 feett

ac motor supply)

• Unit, Power, J86738A, List 1 (MD)--fur-
nished with 551A KSU (MD) • Cord, Power, 824013296, 6 feett

• Unit, Power, 28Al--furnished with 551B
KSU (MD) • Cord, Power, 824010995, 12 feett

• Unit, Power, 28D2--furnished with 551C e Plate, Adapter, 8148626115
KSU *For 551A KSU (MD).

• Lamp, 51A

• Fuses, Bussman, MDL-1 (1 ampere, one per
power unit) :[:For mounting two single width or one double width

• Fuses, 24E (1/2 ampere, three per power
unit) Order required combination of up to four of the

• Fuses, 24B (3 ampere, one per power unit)

• $Tag, Cord, Power--KS-22453.4 four)

• Cord, Power, 824013270, 2 feett

• Cord, Power, 834167678, 4 feet*

• Cord, Power, 834167686, 6 feet*

tFor 551B KSU (MD) or 551C.

1A KTS angle bracket-type KTUs in 550-type KSU.

following KTUs, subject to specified limitations:

• Unit, Telephone, Key, 400H (maximum of

(c) Replaceable (Optional) Components: • Unit, Telephone, Key, 401-Type (maximum of

• Interrupter, KS-19385, List 1 (MD) (requires
24-volt dc motor supply) • Unit, Telephone, Key, 415-Type (maximum of

• Interrupter, KS-19385, List 2 (requires
24-volt dc motor supply) • Unit, Telephone, Key, 467A (maximum of

• Generator, Frequency llSA--for use with one)
550B, 550C, 551B, and 551C KSUs; 105-volt ac
ringing supply (supplied with three mount-

ing screws)

• Bracket, Mounting, 841720857--for mounting units, while 551 types are factory-equipped
llSA frequency generator on 550/551C KSU with plug-in power units:

• Kit of Parts, D-180699 -- for mounting 118A 551C--28D1 (MD) or 28D2 Power Unit
frequency generator on 550/55IB KSU.

(d) Associated Apparatus (order separate-

ly): 551A (MD)--J86738A, List 1 Power Unit

• Cord, Power, 834167652, 1-1/2 feet*

• Cord, Power, 824013262, 1-1/2 feett for 400-series KTUs, two separate jacks for a

Page 2

four)

three)

2.04 Design Features

• 550-type KSUs do not have internal power

551B (MD)--28A1 Power Unit

(MD).

• The basic KSU assembly contains four jacks

ISS 2, SECTION 518-215-407

plug-in KS interrupter and a plug-in power power, line, and station cables. Dress wires along the
unit, and a factory-wired connecting block sides of the connecting block. In the "A" and "B"
with "quick-clip" terminals. KSUs, cable and wire may enter from top or bottom.

• All external connections are made on front of A. Installation

connecting block.

• The 10-volt ac operated KS-19175, List 1 in- dry, vertical surface where it is easily accessi-

terrupter furnished with each KSU provides ble for service (mounting hardware to be obtained
lamp flash, wink, and audible signal feature locally depending on mounting surface). If the KSU

interruptions. It is a plug-in unit locked into has a built-in power unit or if it is to be equipped with
place by a captive screw, cord length of a grounded ll7-volt 60-Hz power outlet

• A 24-volt dc operated KS-19385, List 1 (MD) cord lengths). The outlet should be separately fused

or List 2 interrupter can be substituted for and not under the control of a switch. A KSU without
the one furnished with the KSU at locations built-in power unit should be mounted as close as

where only 24-volt dc power is available, possible to the separate telephone company power

• Intended for vertical mounting on a wall or
other suitable surface. Warning: Do not connect the KSU to

• Protective front and back covers provided, eomplete and all KTUs are installed.

• 550C and 551C have line status lamps which 3.03 External AC Power Cord: An external ac

display the same signals as the line lamps at power cord is required with all 551-type KSUs
associated stations, and with any KSU equipped with a frequency genera-

• 550C and 551C are 17.18 inches high, 9.7
inches wide, and 7.12 inches deep. Note: I_A KS-22453 power cord tag should be

• 550B/551B (MD) and 550C/551C can be receptacle.0
equipped with a 118A frequency generator

which provides power for operating ringers (a) 550/551C KSUs: Open the cable clamp in
at associated stations. Earlier type KSUs the lower left corner of the KSU and insert the
must be connected to an external ringing sup- receptacle end of the external power cord into the

ply. trough; secure the cord with the clamp.

3.02 Mounting: Mount the KSU on a clean, firm,

a l18A frequency generator, it must be located within

provided by the customer (see Ordering Guide for

source.

external power until all other wiring is

tor.

snapped on the ac power cord at the ac

• Common audible signaling can be provided (b) 551B KSU (MD) Only: The 551B KSU ,is
by appropriate strapping on the connecting shipped with its power unit cord carried

block, the KSU case. To install an external power cord:

3. INSTALLATIONAND CONNECTIONS (1) Compress the grommet to release it from

3.01 The information in paragraphs 3.02 through

3.17 applies specifically to the 550C and 551C (2) Remove the grommet from the internal

KSUs, and also to the 550A, 551A, 550B, and 551B
KSUs (all MD), unless otherwise noted. Most new

installations will involve the "C" KSUs, but the MD (3) Insert the receptacle end of the external
units will be encountered in existing installations, power cord through the cutout in the hous-

For methods of strapping and terminating wire and ing where the grommet was removed.
cable, refer to Section 461-604-100. Cables and wire

must be brought into the 550C and 551C KSUs from (4) Place the grommet around the external
the bottom. Clamps are provided for retaining the power cord.

through an insulating grommet in the bottom of

the case.

power cord.

Page 3

SECTION518-215-407

(5) Seat the grommet in the cutout, again from 55oc KEYSERVICEUNITiS

inside the case. CONNECTOR NOTHAVEPOWERUNIT.

POWER UNIT SAME AS 55lC EXCEPT iT DOES

NOTE:

(6) Connect the external power cord to the

power unit cord.

551B KSUs for improper installa-

tion of grommets and power cords

Inspect existing installations of

(ie, grommet around power unit

cord). Correct where necessary.

(c) 551A KSU (MD): Connect the external

power cord to the power unit cord through the

cutout in the bottom of the KSU case.

3.04 Frequency Generator. Install the l18A CONNECTrN.,.,

frequency generator on the 550/551C KSU as

BLOCK

described in (a) or on the 550/551B as described in
(b). Connect as described in paragraph 3.07.

(a) Attach the generator to the mounting bracket

(841720857) with the three screws supplied
(Fig. 1). Snap the pins of the bracket arms into the
holes in the backboard flanges of the KSU. Let the

generator rest against the front of the interrupter
with its power cord to the left. Connect the feed-
through type plug to the external ac power cord

and, if the KSU is a 551C, to the power unit cord.

(b) To mount a 118A frequency generator on a (S_NGL.EPOINT

LOC GRO TERM

550/551B KSU, first install D-180699 Kit of GROUND)

Parts. Remove the cable clamp provided with the _4_720857
KSU and replace it with the one in the kit. Mount BRACKET
the bracket on the door of the KSU as shown in CABLECLAMP liSA FREQUENCY

Fig. 2. Attach the frequency generator to the Ac POWER
bracket with the three screws supplied with the CORD

FOR EXTERNAL GENERATOR

generator. Connect the feed-through type plug to
the external ac power cord and, if the KSU is a
551B, to the power unit cord [see paragraph 3.03(b) Fig. 1--1_551C KSU With Frequency Generator_l

for instructions on positioning the grommet].

B. Connections 550-type must be wired to a suitable external power

3.05 Table A provides a key to the connection dia-

grams in this section for the various models of

supply for all operating voltages. Make all external
power lead connections to the terminals in the D or

the 550/551 KSUs. E columns on the front of the connecting block.

3.06 Internal Power: The 551-type KSUs have _ I£ an external power source is to be

mally require no internal power wiring by the in- minimum 20-volts dc signal battery

built-in, factory-wired power units, and nor- _ used, be sure that it can supply the

staller unless 105-volt ac ringing voltage is required required by 400-series KTUs. I[ it
(see paragraph 3.07 for details). The KSUs of the cannot, convert the KSU to a

Page 4

ISS 2, SECTION 518-215-407

CABLE CLAMP AND

BRACKET iNCLUDED IN
D--180699 KIT OF PARTS

Fig. 2--551B KSU (MD) With 118A Frequency Generator Installed

IIBA FREQUENCY
GENERATOR

Page 5

SECTION518-215-407

TABLE A

CONNECTION DIAGRAM INDEX

550/551C 550/551B(MD) 550/551A(MD)

Terminal Layout
with Station and Fig. 3 Fig. 4 Fig. 4

Line Connections

Power Connections Fig. 5 Fig. 6 Fig. 7

Common Audible
Connections Fig. 8 Fig. 10 Fig. 10

Common Audible
Auxiliary Control Fig. 9 Fig. 11 Fig. 11

Connections

Manual Intercom
Connections

Lead Designations Fig. 12 Fig. 12 Fig. 12

551-type by installing an appropri- naling from several lines. Common audible signaling
ate power unit (see Ordering Guide). is provided by strapping together the appropriate R1

3.07 Audible Signaling Voltage: Audible sig- voltage to the RG and RB terminals. Auxiliary con-
naling can be provided at the stations associ- trol of common audible signaling is possible through

ated with the KSU on either the ringer or the buzzer the use of a separately mounted 227-type $or 421Ai
at each telephone set. Ringer voltage must be sup- KTU wired to the connecting block.

plied from a separate 105-volt ac source, such as the

l18A frequency generator, connected to the RG and 3.09 Line Connections: Connect the incoming
RB terminals on the front of the connecting block. CO/PBX lines to the T-R terminals (43 to 50)

Buzzer voltage can be derived from the 18-volt ac in the A column of the connecting block. The KSU can
audible signal supply available at the internal or ex- accommodate a maximum of four lines.
ternal power unit. Connect buzzer voltage by install-

ing straps from terminals G+ and S+ to RG and RB, 3.10 Station Connections:Terminate the station
respectively, cables on the connecting block, the first cable

Warning: Do not use the 18-voIt ac sup- mum of five stations can be wired directly to the

ply to operate KS-20419, L1 buzzer sup- KSU. If more stations are required, use loop-through
plied in key telephone sets. Doing so will terminations or provide distribution facilities. Con-

result in damage to the buzzer. If nect the ringer or buzzer leads of the station cables
KS-20419, L1 buzzers are to be used, to the B1-R1 terminals.

strap the RG and RB terminals to the LG

and LB terminals, respectively (l O-volt C. Manual Intercom

ac lamp power supply).

3.08 Common Audible: This feature allows mul- 401-type KTU in the KSU. In early production

tiple stations to receive incoming call signals models of the 550/551C KSUs, only jack J4 was facto-

from the same line and a single station to receive sig- ry-wired with the talk (A) battery and ground re-

See 3.11 See 3.13 See 3.13

leads at the connecting block and wiring signaling

on column A, the second on column B, etc. A maxi-

3.11 This feature is provided by installing a

Page 6