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 TM 55-1905-219-14-9
4-46.3. LOUD HAILER - MAINTENANCE INSTRUCTIONS (Continued).
(g) When using the loud hailer it will be observed that the output is noticeably sensitive to
both the strength of the voice and the distance between the talker's lips and the microphone diaphragm. It is
essential, therefore, that the operator speaks in a strong command voice and as close to the microphone
protecting grille as possible - if part of the face touches the aperture it is protected from injury by the rubber
mouthpiece. It is perhaps safer when operating on the deck of a vessel at sea to keep part of the rubber
mouthpiece in contact with the area near the talker's mouth. However the microphone aperture must not be
closed off substantially by the mouth as this will tend to muffle the voice, and may induce acoustic feedback.
(h) The tendency for acoustic feedback to occur is reduced to the greatest practical extent
in this loud hailer. Generally it will not be a problem, but certain conditions of use or operation will tend to start
howling or squealing. For instance, the slotted openings in the microphone housing are an important part of the
design that provides the required margin against acoustic feedback. The operator should never cup one of his
hands around the microphone grille when the unit is activated, as this partially closes off some of these slots.
Acoustic feedback will also tend to start if the horn is directed down to the deck or directed close to a hard wall
or bulkhead. These conditions should be avoided in operation. If however they are unavoidable, as for
instance when it is necessary to use the loud hailer below decks, the volume control knob is backed off (turned
counterclockwise) until the feedback stops, then advanced gradually until a point is reached where maximum
volume without feedback is obtained.
(2) Preparation for Use. No preparation is required to use this loud hailer unless it is desired to use an
external 12 volt storage 'battery to conserve the internal batteries. To use this external supply first operate the
toggle switch in the handle to "EXT". Plug the external battery cable connector into the receptacle in the base
of the handle and screw up the locking ring. Connect the battery clip marked "plus" to the positive post of the
battery and the one marked "minus" to the negative 12 volt post. The unit is now ready for use.
(3)
Operating procedures.
(a) This loud hailer is designed to perform one function - to amplify the human voice with
good intelligibility so that speech can be understood by personnel either over distances too far for the unaided
voice to be understood or in noisy areas where the human voice cannot override the interfering noises.
4-1167
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