1-7.
Installation and Operating Instructions
H-136/AIC earphone ................. 20 ohms.
a. Headset Installation.
M-87/AIC microphone ............... 5 ohms (nominal).
(1) Extend
the
microphone
boom
Headset (two earphones
assembly to its outer limit by loosening the knurled
in parallel) ............................ 10 ohms.
boom-adjusting nut.
Microphone dc resistance ......... 3.5 ohms (nominal).
Earphone audio output level ..... 115 to 120 db
WARNING
above 1
Unless a good acoustic seal is
milliwatt.
achieved, the hearing of a wearer, in
the noise environment for which the
headset filters to out-
headset is designed, can be
side noise ............................. 31 db at 1 kHz.
permanently damaged.
1-6.
Description
(2) Place the headset on the head. The
Headset-Microphone 19LB-87 is composed of the
correct position of the headband is slightly forward of the
assemblies described in a through f below.
highest point of the head when the wearer is looking
a. Headband Assembly.
The headband
straight forward. The correct position of the headband is
assembly consists of a spring steel band with sliding
such that when the wearer pulls downward on both
hardware, two stirrups, top pad with nomenclature label,
domes, the headband pulls straight down without a
a foam headpad, and an overhead cord. The headband
tendency to move forward or behind its resting place.
assembly provides the correct force and mechanical
The headset must be properly positioned to obtain a
adjustment to fit nearly every shape of human head and
good acoustic seal.
retain the necessary acoustic seal.
b. Microphone Installation.
b. Dome Assembly, Right. The right dome
assembly consists of a plastic dome which attaches to
CAUTION
the stirrup with two retaining rings. Within the dome
Never use the microphone more than
shell is an earphone assembly (an H-136/AIC earphone
one-fourth of an inch from the
plus coupler), a retaining ring, and a foam acoustic pad.
speaker's lips.
Affixed to the outside of the dome shell is an ear seal
and a ring of plastic foam covered by a vinyl plastic film.
(1) With the microphone-headset properly
c. Dome Assembly, Left.
The left dome
positioned on the wearer's head, fold the microphone
assembly consists of the same components listed in b
boom assembly so that the microphone is positioned in
above, plus the boom guide assembly, a microphone
front of the wearer's lips. The correct position for the
jack cord, and an attached telephone plug cord
microphone is slightly off-center and barely touching the
assembly.
lips.
d. Boom Assembly. The boom assembly
consists of a two-section, hinged wire boom which
CAUTION
carries the M-87/AIC microphone, the microphone
Overtightening the knurled boom
extension cord, and the microphone cord retainer. It is
guide assembly nut can break the
attached to the left dome assembly by the boom guide
plastic shell of the left dome
assembly.
assembly.
e. Telephone Plug Cord Assembly.
The
telephone plug cord assembly consists of a length of
(2) With
the
microphone
properly
four conductor cord, one end with the conductors joined
positioned, tighten the knurled boom guide nut until the
to connectors within the left dome assembly, and the
boom assembly is held securely in place.
other end fitted with a U-93A/U connector plug.
c. Operating Procedure. Insert the U-93A/U
f.
Boom Guide Assembly. The boom guide
connector plug into the proper receptacle on the
assembly provides the hardware for attaching the
equipment, or into a U-94A/U plug connector with an
microphone boom assembly to the left dome shell. It
extension cord.
The headset-microphone is then
incorporates the mechanical adjustments for positioning
capable of continuously sending and receiving audio
the boom assembly.
information. Use of a U-94A/U plug connector is
desirable in a high-noise level environment as it can
provide push-to-talk operation.
6
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