to center around the emitting frequency of the acoustic training device and to amplify the microphone output the output pin 8 of the quad amplifier 200 is fed to the input pin 3 of phase lock loop 202 the phase lock loop 202 is configured as a narrow band tone detector the output pin 8 of the phase lock loop 202 goes low when a signal of the proper frequency is presented to the input pin 3 of the phase lock loop 202 the output pin 8 of the phase lock loop going low causes the base on transistor 208 to go low which allows capacitor 210 to charge if the output pin 8 of the phase lock loop 202 stays low long enough for capacitor 210 to charge beyond a set threshold power supplied by pin 3 to the miles through timer 204 is removed the miles is thus supplied power through the output of timer 204 in place of the normal battery in the miles power remains removed from the miles until the acoustic signal is no longer received from the acoustic training device when the acoustic signal is no longer being received power is restored to the miles and the tampering circuit activates an internal.