With this circuit, we can have a acoustic clue, frequency 2KHZ, when we have a short vibration in his entry. It is constituted from monostable multivibritor (with schmitt trigger inputs), with duration roughly 100msec, oscillator TTL, that oscillating in their 2KHZ and one rung of expense a loudspeaker or piezoelectric element. The square vibration that is applied in his entry, trigger his multivibritor that with line drive the oscillator and his the loudspeaker. With switch S1, we can select the polarity of vibration of entry, if this is positive or negative. The frequency of oscillator can change, if we change the capacitor C4 or resistance R2, so that changes also the frequency of sound that we hear from the loudspeaker and with the TR1 we alter the intensity of him tone in the loudspeaker.
The power supply is + 5V.
R1= 68Kohms C1= 2.2uF 16V D1= 1N4148
R2= 1.2Kohms C2-4= 100nF 100V Q1= BC550
R3= 4.7Kohms C3= 47uF 16V LSP= 8ohms 0W25 Loudspeaker
R4=100ohms IC1= 7400 S1= 1X2 mini Switch
TR1= 1Kohms trimmer IC2= 74121 All Resistors is 1/4W 1% or 5%