BELL SYSTEM PRACTICES
AT&TCo Standard
SECTION 502-541-407
Issue 3, June 1973
SERVICE
564HK AND 564HL TELEPHONE SETS
1.
GENERAL
1.01
This section contains connection and maintenance
information on the 564HK (MD) and 564HL
telephone sets.
1.02
This section is reissued to include information
on A20B connector cable.
2.
MAINTENANCE
2.01
The 564HK set with D30C cord may be
subject to poor key button illumination in
multiple station, long loop situations due to the
omission of lamp ground straps on the cord plug.
2.02
When investigating poor key button illumination
involving 564HK telephone sets:
(a) If the station termination is made on a
66E3-25 or 66E4-25 connecting block,
loop-through straps can be installed on connecting
block clip terminals 5,
11, 17,
23, and 29 to add
the necessary lamp ground copper for lamps 2,
3, 4, and 5. In all cases, full pairs should be
brought to the connecting block from connecting
key system apparatus via inside wiring or A-type
connector cables.
(b) If station termination is made via •A20B•
connector cable, or at a 3-way bridging
adapter, or equivalent, it is impractical to
field-modify either the plug of the D30C telephone
set cord or its mating connector on the A-type
connector cable. Therefore, the 564HK should
be replaced with a 564HL.
2.03
Remove and replace housing as follows:
(1) To remove housing, loosen captive screws
in base of set. Lift housing up and toward
front of set.
(2) To replace housing, guide lower front of
housing over pushbuttons, align housing with
base of set, and gently press housing into place.
Tighten captive screws in base of set.
2.04
Replace cracked pushbuttons or collars.
Remove accumulated dirt or film from lamps,
collars, and pushbuttons with a water dampened
cloth.
DO NOT USE SOL VENTS OF ANY
KIND.
If cleaning does not correct binding of
pushbuttons, replace button and collar assembly.
2.05
Maintenance of handsets, dials, and ringers
is outlined in sections covering these
components.
2.06
When replacing a defective lamp use a
KS-6320 orange stick to extract the lamp
from its socket, and install the new lamp with its
contact surfaces properly aligned with the lamp
socket.
2.07
Maintenance of the 636-type key consists of
cleaning contacts with a 265-type tool, and
checking for loose or broken connections.
It
No field m aintenance sho uld be
performed on the plug of plug-ended
mounting cords.
2.08
Replace set if the following requirements
cannot be met:
(a) When depressed locking plunger should, on
its downstroke, release any previously locked
plunger.
(b) When any pushbutton plunger is released
from its operated position, it should return
with a snap to its nonoperated position.
(c) An operated key plunger should not release
during downstroke of hold button.
(d) An operated key plunger should release from
its operated position on the upstoke of the
hold button.
© American Telephone and Telegraph Company,
1973
Printed in U.S.A.
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