Electronic siren system

Claim 2

An electronic siren system for operating a sound producing transducer, which comprises: a direct current constant voltage source; a basic oscillating circuit including a resistancecapacitance circuit, said basic oscillating circuit being connected across said direct current constant voltage source and generating an output having a frequency determined as a function of the time constant of said resistance-capacitance circuit and the value of the voltage applied to said basic oscillating circuit; means for varying the frequency of the output of said basic oscillating circuit including a modulating oscillator connected across said direct current constant voltage source for generating a varying modulating voltage output, and means for applying said varying modulating voltage to said basic oscillating circuit for varying the frequency of the output of said basic oscillating circuit as a function of the variation in the modulating voltage; said modulating voltage applying means including a semiconductor device connected between said direct current constant voltage source and said basic oscillating circuit, and means coupling said semiconductor device to said modulating oscillator for applying said varying modulating voltage to said semiconductor device, said semiconductor device varying the voltage applied to said basic oscillator circuit in response to and as a function of the variation in said modulating voltage to effect variation in the frequency of the output of said basic oscillating circuit.

Claim 3

An electronic siren system as described in claim 1, in which said semiconductor Device comprises a transistor, means connecting the emitter-collector circuit of said transistor between said direct current constant voltage source and said basic oscillating circuit, and said coupling means connecting the base of said transistor to the output of said modulating oscillator.

Claim 4

An electronic siren system as described in claim 2, in which said modulating oscillator includes a relaxation oscillator comprised of a unijunction transistor and a resistance-capacitance circuit connected to a base-emitter circuit of said unijunction transistor to produce said modulating voltage in the form of a sawtooth output at the emitter of said unijunction transistor; and wherein said coupling means connects the base of said transistor to the emitter of said unijunction transistor.

Claim 5

An electronic siren system as claimed in claim 2, in which said modulating oscillator includes two relaxation oscillators each comprised of a unijunction transistor and a resistance-capacitance circuit connected to the base-emitter circuit of said unijunction transistor to produce said modulating voltage in the form of a sawtooth wave output at the emitter of said unijunction transistor; wherein the frequency of the modulating voltage output of one of said relaxation oscillators is different than the frequency of the modulating voltage of the other of said relaxation oscillators; and wherein said coupling means includes switching means for selectively connecting either or both of said relaxation oscillators to the base of said transistor.

Claim 6

An electronic siren system as described in claim 1, and further including a push-pull amplifier adapted to apply the output of said basic oscillator circuit to the sound producing transducer; and a semiconductor phase inverter coupling said basic oscillating circuit output to said push-pull amplifier.

Claim 7

An electronic siren system as described in claim 5, wherein said push-pull amplifier includes a first transistor and a second transistor, and said phase inverter includes a transistor, means coupling the collector of said phase inverter transistor to the base of said first transistor and means for coupling the emitter of said phase inverter transistor to the base of said second transistor, whereby the signal at the base of said first transistor is 180* out of phase with the signal at the base of said second transistor, and means coupling the base of said phase inverter transistor to the output of said basic oscillating circuit.

Claim 8

An electronic siren system as described in claim 6, including first and second output transistors having their collectors connected across a common output transformer and their emitters coupled to a common point, means for coupling the emitter of said first transistor to the base of said first output transistor and means for coupling the emitter of said second transistor to the base of said second output transistor, and means for balancing the signals at the collector and emitter of said phase inverter transistor, whereby the base signals of said first and second output transistors are equal.

Claim 9

An electronic siren system as described in claim 7, said balancing means comprising a resistance connected to the emitter of said phase inverter transistor and a resistance connected to the collector of said phase inverter transistor.

Claim 10

An electronic siren system comprising: a direct current constant voltage source; a multivibrator including a pair of transistors and a resistance-capacitance circuit, said multivibrator being connected across said direct current constant voltage source and generating an output having a frequency determined as a function of the time constant of said resistance-capacitance circuit and the value of the voltage applied thereto; a pair of modulating oscillators generating varying modulating voltage outputs of different frequencies; means for selectively connecting said modulating voltages from either or both of said modulating oscillators to said multivibrator to vary The frequency of the output thereof as a function of the variation of the applied voltage including: a transistor having its emitter-collector circuit connected in series between said direct current constant voltage source and said multivibrator and, switching means for selectively connecting the base of said transistor to either or both of said modulating oscillators, said transistor varying the voltage applied to said multivibrator in response to and as a function of the variation in the modulating voltage applied to its base to effect a variation in the frequency of the output of said multivibrator; a transistor phase inverter circuit, means coupling the base of said phase inverter transistor to the output of said multivibrator; a push-pull transistor amplifier including first and second transistors, means connecting the base of said first transistor to the collector of said phase inverter transistor and means connecting base of said second transistor to the emitter of said phase inverter transistor, whereby the signal at the base of the first transistor is 180* out of phase with the signal at the base of the second transistor; a sound producing transducer, and means connecting said sound producing tranducer to the output of said push-pull amplifier.

Claim 11

An electronic siren system comprising: a direct current constant voltage source; a multivibrator including a pair of transistors and a resistance-capacitance circuit, said multivibrator being connected across said direct current constant voltage source and generating an output having a frequency determined as a function of the time constant of said resistance-capacitance circuit and the value of the voltage applied thereto; a pair of modulating oscillators generating varying modulating voltage outputs of different frequencies; means for selectively connecting said modulating voltages from either or both of said modulating oscillators to said multivibrator to vary The frequency of the output thereof as a function of the variation of the applied voltage including: a transistor having its emitter-collector circuit connected in series between said direct current constant voltage source and said multivibrator and, switching means for selectively connecting the base of said transistor to either or both of said modulating oscillators, said transistor varying the voltage applied to said multivibrator in response to and as a function of the variation in the modulating voltage applied to its base to effect a variation in the frequency of the output of said multivibrator; a transistor phase inverter circuit, means coupling the base of said phase inverter transistor to the output of said multivibrator; a push-pull transistor amplifier including first and second transistors, means connecting the base of said first transistor to the collector of said phase inverter transistor and means connecting base of said second transistor to the emitter of said phase inverter transistor, whereby the signal at the base of the first transistor is 180* out of phase with the signal at the base of the second transistor; a sound producing transducer, and means connecting said sound producing tranducer to the output of said push-pull amplifier.