The tone of a call tone device is produced by a positive feedback common emitter amplifier and transducer arrangement. Voltage supply to the tone generator is interrupted cyclically by an astable multivibrator with timer circuit to provide an intermittent call tone.

A personal noise making and alarm signal device which can be worn in the pocket of a garment, comprising two concave parts opposingly connected together at their peripheries. Within the enclosure is an electric sound producing device, including an electromagnetic speaker, sounding board means carried by the electromagnetic speaker and by one of the parts, a cone carried by one of the parts and having its small opening lying close to the loud speaker device and a combined battery and push button ...

The invention is an electronic siren comprising in combination means for generating periodically occurring charging pulses at a selected one of a plurality of predetermined repetition rates, time-constant determining means coupled to the pulse generating means for generating a repeating voltage wave form in response to the charging pulses and means coupled to the time-constant determining means for generating a square wave signal having a frequency proportional to the instantaneous voltage of th...

Apparatus and method for repelling rats and mice from an area by means of generation of a modulated ultrasonic sound level. The sound level is frequency modulated within a range of ultrasonic frequencies to which rats and mice respond. In addition, it is amplitude modulated in a random manner. The modulations of the signal prevent rats and mice from adapting to the sound, and thereby renders the sound particularly unpleasant to them.

Variable audiofrequency signals for use in alarms, entertainment devices and like applications requiring sonic outputs from rugged and economical miniaturized equipments which consume little power, are provided by a transistorized circuit wherein sinusoidal outputs from a simple phase-shift oscillator govern the frequencies at which a voltage-controlled audio oscillator drives its load in the form of a voice coil of an inexpensive loudspeaker.

Electronic audible signal devices such as doorbells, buzzers, beepers, telephone bells, school bells, bicycle bells, sirens, signaling bells in general and signalling devices in general are provided by novel combinations of random voltage generators, voltage controlled tone generators, pulsers, triggers, pulse shapers, keyers, audio generators, delay devices, amplifiers and loudspeakers.

Apparatus for producing an audible signal when a voltage is applied thereto. The apparatus includes a reed switch having electrical contact leads, means responsive to the voltage to cause the switch to open and close periodically whereby the leads vibrate, and means responsive to the vibration to produce said signal.

An electronic arrangement for simulating sounds emitted by animals. A clock ulse generator transmits pulses which are partially differentiated and/or integrated. The resulting pulse signals are applied to a series of astable multivibrator circuits which synthesize audiofrequency signals representing the various types of animal cries. Multivibrator circuits may be combined with each other in a particular arrangement, and these combinations may be operated in conjunction with variable integrating ...

An electric sound producing device includes a ferromagnetic diaphragm, an electromagnet for deforming the diaphragm and an oscillator for repeatedly supplying short duration current pulses to the electromagnets. The oscillator may be driven by a multivibrator to produce intermittent sound pulses or by a saw-tooth pulse generator to produce sound with an apparently cyclically varying frequency.

Semiconductor circuits for the automatic generation of tone sequences of different tones. A bistable switch having a control input activated by start signal controls a voltage stabilizing circuit which in turn controls an RC-oscillator. Several frequency dividers are driven by the oscillator for producing divider outputs as tone signal outputs furnishing individual tone frequencies corresponding to the tone sequences to be produced. A general cycle control has inputs controlled by the first divi...