Abstract: A piezoelectric signaling device has an oscillator circuit which includes a transistor amplifier and a piezoelectric transducer. There is a Zener diode in the transistor circuit. The Zener voltage of the diode determines the start-up voltage of the device. By choosing diodes with different Zener voltages, the start-up voltage may be preselected. In other embodiments, the diode may be connected in the base circuit of the transistor or in other portions of the oscillator circuit.

Abstract: A piezoelectric signaling device that produces a predetermined number of audio signals when activated. The device includes a timer, a pulser, an audio oscillator, and a piezoelectric transducer. The timer enables the pulser for a predetermined time. While enabled, the pulser produces pulses at a predetermined rate, thus producing a predetermined number of pulses. The oscillator is enabled during the pulses to produce a predetermined number of pulses of audio frequency electrical oscillations which are applied to the piezoelectric transducer to produce the predetermined number of audio signals.

Abstract: There are three oscillator circuits which oscillate at different frequencies, each oscillator circuit including a gate having an input and an output. The output of the first gate is connected to an inverter and the input of the second gate. The output of the inverter is connected to the input of the third gate. The output of the second and third gates is connected across a piezoelectric transducer to produce a warble sound.