TM 55-1930-209-14&P-12
1.1.3
Continued
The transformer T1 and resistor R12 is selected at manufacture to provide this frequency. When the driver
unit and horn are connected the following changes take place in the above sequence of events:
At the instant Q7 starts to conduct, the coil on the driver starts to move. Since the natural period of the
mechanical suspension is 390 HZ, the coil reaches its maximum position and starts to reverse its motion
when approximately half of the free-running Q7 "on" time has expired. As soon as the coil stops moving, it
represents a virtual dead short on T2, causing the output voltage to suddenly drop to zero. This sudden
change when amplified by Q6 causes Q7 to turn off and consequently Q8 to turn on prematurely. The net
result is a sudden change in the frequency of the oscillator. The frequency is now controlled by the motion
of the driver-coil. The remaining components are to remove voltage transients caused by the sudden
changes in current in T2, and to provide the necessary bias current and driving circuits for Q6, Q7, and Q8.
The net result of the previously described sequence of events is to cause the coil and hence the diaphragm
on the driver unit to oscillate at its natural period. The oscillator has changed the battery current (D.C.) to
alternating current (A.C.) and at the same time has approximately doubled the voltage. Due to this
doubling action, when 10 volt D.C. is supplied to the oscillator, the alternating current output will be
approximately 20 volts from
Form No. 6310 0238
viii
