Electronic siren

Claim 2

Apparatus for generating an electrical signal which varies at an audible frequency comprising: controllable oscillator means; remote control means, said remote control means including a mode selector switch and encoder means for generating a binary coded output signal commensurate with the setting of said mode selector switch; decoder means, said decoder means being located remotely from said remote control means and being responsive to the coded output of said remote control means for generating a plurality of gate control signals; means delivering the coded output of said remote control means to said decoder means; gate circuit means responsive to the control signals generated by said decoder means, said gate circuit means including switch means connected to said oscillator means, said gate circuit means changing the frequency and rate of change of frequency of said oscillator means output signal commensurate with the setting of said remote control means mode selector switch; amplifier means; means applying said oscillator means output signals as the input signal to said amplifier means; and means for delivering signals amplified by said amplifier means to a loudspeaker.

Claim 3

The apparatus of claim 1 wherein said oscillator means comprises: a first oscillator, said first oscillator simultaneously producing output signals having at least two wave forms, said first oscillator output signals being variable between a plurality of preselected frequencies in response to the gate control signals of said decoder means; a voltage controlled oscillator, said voltage controlled oscillator generating output pulses at a repetition rate commensurate with the magnitude of an input signal delivered thereto, the output signals of said first oscillator being selectively delivered as input signals to said voltage controlled oscillator under the control of said decoder means; and means responsive to the pulses generated by said voltage controlled oscillator means for producing a symmetrical alternating signal at a frequency which varies with the output frequency of said voltage controlled oscillator.

Claim 4

The apparatus of claim 2 further comprising: means for manually varying the output frequency of said oscillator means, said manual frequency varying means including: manual switch means, said manual switch means providing a steady state output signal when in the closed condition, said manual switch means being connected to said remote control means encoder means whereby the closing of said manual switch means will cause the coded output signal of said remote control means to vary; timing circuit means, said timing circuit means being responsive to the state of said gate circuit means commensurate with the coded output signal of said remote control means corresponding to closing of said manual switch means to provide a voltage which varies with time, said time varying voltage being applied by said gate circuit means to said voltage controlled oscillator; comparator means, said comparator means comparing the output of said timing circuit means with a preselected bias voltage level commensurate with a minimum oscillator output frequency, said comparator means providing an output signal when said oscillator output frequency reaches the said minimum; and means for disabling said oscillator means in response to said comparator means output signals.

Claim 5

The apparatus of claim 3 further comprising: means responsive to input signals of either polarity for generating command signals; bistable circuit means responsive to said command signals for generating a further gate control signal; and means for delivering said further gate control signal to said gate circuit means to cause the output of said oscillator means to change.

Claim 6

The apparatus of claim 4 wherein said remote control means further comprises: means responsive to the closing of a switch in a microphone, the microphone being coupled to said remote control means, for applying a further input signal to said encoder means whereby said encoder means will generate a binary signal commensurate with the disabling of said oscillator means; means for passing audio frequency signals provided from a microphone, said signal passing means including a variable attenuator; and means for delivering said passed signals to said amplifier means regardless of the position of said mode selector switch.

Claim 7

The apparatus of claim 1 wherein said remote control means further comprises: means responsive to the closing of a switch in a microphone, the microphone being coupled to said remote control means, for applying a further input signal to said encoder means whereby said encoder means will generate a binary signal commensurate with the disabling of said oscillator means; means for passing audio frequency signals provided from a microphone, said signal passing means including a variable attenuator; and means for delivering said passed signals to said amplifier means regardless of the position of said mode selector switch.

Claim 8

The apparatus of claim 1 further comprising: means responsive to input signals of either polarity for generating command signals; bistable circuit means responsive to said command signals for generating a further gate control signal; and means for delivering said further gate control signal to said gate circuit means to cause the output of said oscillator means to change.

Claim 9

The apparatus of claim 1 wherein said amplifier means comprises: an output transformer, said transformer including a centertaped primary winding, a secondary winding and a feedback winding, said feedback winding being connected to said means for delivering signals to a loudspeaker; a pair of output transistors, said output transistors each including a base, a collector and an emitter, said output transistors and said transformer primary winding being connected to define a push-pull amplifier stage; preamplifier means, said preamplifier means including first and second drive transistors connected as emitter followers, the emitters of said drive transistors being respectively coupled to the base of an output transistor, the bases of said drive transistors being connected to said means for applying oscillator means output signals to said amplifier means; and means connecting the collectors of said drive transistors to respectively opposite ends of said transformer feedback winding, the voltages appearing at the emitters of said drive transistors being commensurate with the associated collector voltage and each having a polarity which will increase conduction of the associated output transistor, said voltages increasing with the average magnitude of the oscillator means output signals applied to the bases of said drive transistors whereby said output transistors will be driven into saturation with input signals of greater than a predetermined magnitude.

Claim 10

The apparatus of claim 8 wherein said drive transistors share a common collector resistor.

Claim 11

The apparatus of claim 9 wherein said means applying said oscillator means output signals as the input signal to said amplifier means includes: an input transformer having a primary winding and a secondary winding, opposite ends of said input transformer secondary winding being connected to respective of said drive transistor bases, said oscillator means output signals being applied to said input transformer primary winding.

Claim 12

The apparatus of claim 10 wherein said input transformer secondary winding is center-tapped and said apparatus further comprises: a source of constant current; and variable resistance means connected between said input transformer second winding center-tap and said constant current source whereby a constant bias voltage will be applied to said drive transistors.

Claim 13

The apparatus of claim 8 further comprising: means for applying a bias voltage to said drive transistor bases, said bias voltage applying means including a constant current source and resistor means connected to said current source for developing a bias voltage whereby said drive transistors will be non-conductive in the abscence of an input signal from said oscillator means.