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TM 55-1905-220-14-9
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".


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