The regulator is adjusted to give 8 V DC output when 12 V DC is applied to the input. This will maintain a
constant 17.8 watts output from the oscillator with a DC voltage range of 10-14 V DC.
With the application of power to the oscillator-stage of the power supply (which occurs when the timer-
stage codes the regulator "on") the oscillator and fog signal driver (coil and diaphragm mounted in
magnetic field) oscillate as a system at a at a natural frequency of approximately 390 HZ.
The chamber in which the diaphragm moves is designed to operate as one half of an acoustic transformer.
The connecting plumbing and the horn can be considered the other half. The chamber allows the
diaphragm to move a small volume of air at high pressure, and the plumbing and horn transform this into a
large volume at low pressure. The chamber thus allows the small diaphragm to operate at maximum
As the sound enters the main throat of the horn, it divides into two equal parts which are radiated at the top
and bottom of the horn. Along a plane passing through the center of the horn, perpendicular to the vertical
axis, the sound waves will add. This plane represents the maximum sound level available from the horn.
As the angle of radiation increases or decreases with respect to this plane, the sound waves tend to
subtract. This characteristic of the horn results in a horizontal "pancake" of sound with consequent
suppression of vertical radiation.
Form No. 6310 0238