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 TM 55-1905-219-14-9
4-46.3. LOUD HAILER - MAINTENANCE INSTRUCTIONS (Continued).
(2)
Functional Sections.
(a)
D.C. power circuits.
1
12 volt d.c. power is selected from either the internal or external batteries by the operation of the toggle
switch, S2, to the desired position. This does not apply d.c. power to the amplifier however. The
Press-to-Talk switch S1 supplies d.c. power to the amplifier only when it is held closed.
2
The current drain from the batteries is very small when S1 is closed and-no signal is applied to the
microphone. The current is maximum when the loudest signal is being amplified, as the collector
current of the output stage varies with the strength of the amplified signal.
3
External battery power is obtained thru the receptacle J1 into which the external battery cable is
plugged. Both internal and external batteries furnish a nominal 12 volts. The dry cell voltage will fall
off with use while that from the storage battery will remain close to 12 volts until the discharge state is
approached. Somewhat greater power output at a given distortion content is possible with the external
storage battery, because the voltage remains more constant and because the internal resistance is
lower-than that of the dry cell batteries.
(b) Battery cartridge or lung assembly. Eight D size cells (type BA-30) fit into the lung, four on either side
of the separator, on which outlines the cells shown the correct inserting position of each. The lung cover
assembly, contains a contact spring board, similar to that in the lung. This cover assembly is held to the lung'
by four captive scows, with an "O" ring, in the joining surface to prevent entry of water. The upper leg of the
cover and the top leg of the lung are marked "TOP", as the cover assembly must be put on in this orientation so
that the cover contact springs will connect the battery cells correctly. In addition, the upper leg on cover is
longer than the other three, and the recess in the top leg of lung is correspondingly greater to aid in orienting
the cover properly.
4-1173
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