Siren-horn circuitry

Claim 2

Electronic tone-producing apparatus comprising a loudspeaker having a voice coil, means producing potential the level of which is related to pitch of tone desired from said speaker, first and second transistors, means interconnecting said transistors in a double inversion amplifying relationship, means directly connecting said voice coil in the current flow path of said second transistor, a capacitance connected to supply positive feedback between the output of said second transistor and the input to said first transistor, and to cause self-sustaining cyclic operations of said transistors, and means applying potential from said potential-producing means to said capacitance in control of the charging and discharging rates thereof, whereby the periodicity of electrical signals through said voice coil and the pitch of tones produced by said speaker are determined by said potential.

Claim 3

Electronic tone-producing apparatus as set forth in claim 1 wherein said capacitance is of impedance value and said potential is within levels which cause said transistors to be turned on and off cyclically at audio frequency rates, and wherein said means producing said potential comprises an oscillator producing potentials which vary cyclically at a very low frequency which is below audiofrequency, whereby the pitch of tones produced by said speaker varies at said low frequency.

Claim 4

Electronic tone-producing apparatus comprising a loudspeaker having a voice coil, means producing potential the level of which is related to pitch of tone desired from said speaker, a first NPN transistor, a second PNP transistor, means connecting the collector of said First transistor with the base of said second transistor, means directly connecting said speaker voice coil serially with the collector of said second transistor, a capacitance coupling said collector of said second transistor with the base of said first transistor, means applying to the base of said first transistor potential related to the potential from said potential-producing means, and means for applying potential across the series combination of said voice coil and the emitter-collector path of said second transistor, whereby periodic electrical signals are developed through said voice coil and said speaker produces audio tones determined by said potential level.

Claim 5

Electronic tone-producing apparatus comprising a loudspeaker having a voice coil, means producing potential the level of which is related to pitch of tone desired from said speaker, a first NPN transistor, a second PNP transistor, means connecting the collector of said First transistor with the base of said second transistor, means directly connecting said speaker voice coil serially with the collector of said second transistor, a capacitance coupling said collector of said second transistor with the base of said first transistor, means applying to the base of said first transistor potential related to the potential from said potential-producing means, and means for applying potential across the series combination of said voice coil and the emitter-collector path of said second transistor, whereby periodic electrical signals are developed through said voice coil and said speaker produces audio tones determined by said potential level.

Claim 6

Electronic tone-producing apparatus comprising a loudspeaker having a voice coil, means producing potential the level of which is related to pitch of tone desired from said loudspeaker, a first NPN transistor, a second PNP transistor, means connecting the collector of said first transistor with the base of said second transistor, means directly connecting said loudspeaker coil serially with the collector of said second transistor, a capacitance coupling said collector of said second transistor with the base of said first transistor, means applying to the base of said first transistor potential related to the potential from said potential-producing means, means for applying potential across the series combination of said voice coil and the emitter-collector path of said second transistor, said means for applying potential across said series combination comprising a battery, positive potential from said battery being applied to the emitter of said second transistor and the collector of said second transistor being connected with the negative-potential side of the battery through said voice coil, and means connecting the emitter of said first transistor with said negative-potential side of the battery, said means applying potential to the base of said first transistor comprising voltage-dividing resistance connected at one end with said negative side of the battery and at the opposite end with said means producing potential and at position in between with said base of said first transistor, whereby periodic electrical signals are developed through said voice coil and said loudspeaker produces audio tones determined by said potential level.

Claim 7

Electronic tone-producing apparatus comprising a loudspeaker having a voice coil, means producing potential the level of which is related to pitch of tone desired from said loudspeaker, a first NPN transistor, a second PNP transistor, means connecting the collector of said first transistor with the base of said second transistor, means directly connecting said loudspeaker coil serially with the collector of said second transistor, a capacitance coupling said collector of said second transistor with the base of said first transistor, means applying to the base of said first transistor potential related to the potential from said potential-producing means, means for applying potential across the series combination of said voice coil and the emitter-collector path of said second transistor, said means for applying potential across said series combination comprising a battery, positive potential from said battery being applied to the emitter of said second transistor and the collector of said second transistor being connected with the negative-potential side of the battery through said voice coil, and means connecting the emitter of said first transistor with said negative-potential side of the battery, said means applying potential to the base of said first transistor comprising voltage-dividing resistance connected at one end with said negative side of the battery and at the opposite end with said means producing potential and at position in between with said base of said first transistor, whereby periodic electrical signals are developed through said voice coil and said loudspeaker produces audio tones determined by said potential level.

Claim 8

Electronic tone-producing apparatus as set forth in claim 4 wherein said means producing potential comprises a single-transistor phase-shift oscillator producing potentials varying substantially sinusoidally at a frequency which is low relative to frequency of said audio tones, and further comprising switching means for selectably connecting said sinusoidally varying potentials to said opposite end of said voltage-dividing resistance, to cause said speaker to develop cyclically varying siren tones, and for selectably connecting said opposite end of said voltage-dividing resistance with the positive side of the battery, to cause said speaker to develop a substantially fixed tone.