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 TM 55-1905-219-14-9
4-46.3. LOUD HAILER - MAINTENANCE INSTRUCTIONS (Continued).
e. Performance Standards.
(1) Performance standards of the equipment and its supply in terms of resistance measurements, voltage
measurements, and other operating parameters are given in detail in Chapter 5.
(2) However a practical qualitative check of the loud hailer performance can be made at any time without
the use of measuring instruments by giving the equipment a simple operational test.
(a)
Simple operational test.
1
Hold the loud hailer in the normal talking position, operate the trigger switch and advance the volume
control while counting into the microphone "1, 2, 3, 4," etc. The reproduced voice from the horn
should be clear and intelligible at any setting of the volume control and the intensity should increase
gradually as the volume control is advanced. If this test is made in a location free of reflecting walls
or the like, operation should be normal right up to the maximum setting of the volume control without
acoustic feedback causing a howl or squeal.
2
With the volume control still at its maximum setting an indication of the normal amplification may be
obtained by directing the horn towards a hard wall a few feet away or towards a floor. If the
amplification of the loud hailer is up to normal this test will cause the system to break into acoustic
feedback. With a normally functioning unit the acoustic feedback can be stopped by backing off the
volume control from maximum.
3
This test can be made both with the internal batteries as the power source or with an external 12 v
storage battery, so that both battery supply circuits can be checked by this simple operational test. As
described in previous sections, when the internal batteries are used the toggle switch on the back of the
pistol-grip handle should be operated in "INT". To use an external 12 v storage battery connect it with
the battery extension cable to the receptacle in the handle and operate the battery transfer switch to
"EXT".
4-1175
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