Installation - Bell System Practices Plant Series Service

External 670A and 671A are used in conference
2.10
arrangements of 3-type speakerphone:
670A consists of an AC1 transmitter unit,
transistorized amplifier, ON-OFF switch with
2-position ON switch for control of auxiliary
671A transmitters, volume control, plastic
housing, and T9A mounting cord.
671A consists of an AC1 transmitter unit
and used as auxiliary station in conference
arrangement, encased in a plastic housing;
no cord is provided.
In areas where R.F. interference is a problem,
2.11
install a modified 666B or 670A transmitter.
These transmitters have been modified by the
Western Electric Service center.
are identified by a stamp "MOD FOR RF" located
near unit code stamping. Order units as follows:
"Transmitter, 666B or 670A Modified per Specification
X-4200."
2.12 Internal transmitters are all modular, designed
to be an integral part of the telephone set
or console. Connections are made through a KS-type
connector or receptacle block and plugs. Components
are similar to those in external transmitters.
#667B—used in CALL DIRECTOR® sets
equipped with 590- or 650-series keys.
#672A—used in 3640 and 3641 CALL DIRECTOR
telephone sets
#673A—used in nurses console in 3A hospital
interphone system
0674A—intended for use in 3673A-type
telephone set
#674B—use in 2671-type CALL-A-MATIC®
telephone set
0679—used in current production CALL
DIRECTOR sets equipped with 635-type
keys.
Power Supply
2.13 Power to operate the 55-type control units
must be supplied by a 2012B transformer
(ordered separately). Due to lower voltage rating,
a 2012A transformer should not be used.
3.
3.01
requirements:
(1) Provide a set of line switch transfer contacts
handset is lifted.
(2) Rotary dial sets dialed in an on-hook condition
contacts in the dial for loudspeaker and receiver
muting during dialing.
(3) TOUCH-TONE sets dialed in the on-hook
(s and t) in the dial common switch to connect
Modified units
line power (IR) from the control unit to the dial
oscillator. If a polarity guard is provided these
contacts (s and t) must be isolated from the
oscillator by the polarity guard.
3.02
(1) Avoid placing apparatus with plastic covers
may exceed 140 degrees F.
(2) Control unit chassis is part of the electrical
surface.
(3) Control unit can be located a maximum of
(transmitter, loudspeaker, etc.) when (Al) leads
are connected between both the control unit
and transmitter and the control unit and the
telephone set.
(4) Locate transformer no more than 100 feet
not be controlled by a switch.
(5) Place loudspeaker and transmitter within
3 feet spacing between the units and not facing
one another.
(6) There should be no obstructions between
(7) To prevent inductive interference on conference
ISS 5, SECTION 512-620-100

INSTALLATION

The telephone set intended for use in 3-type
speakerphone system must meet the following
to disconnect the speakerphone when the
must provide two sets of off-normal (make)
condition must provide a set of make contacts
Planning an installation:
or parts in locations where ambient temperatures
circuit and must be mounted on an insulated
100 feet from other system components
from control unit. The AC receptacle should
convenient reach of user and with nominal
the user, loudspeaker, and transmitter.
system installations, use no more than 30
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