A fail-safe electronic comparator circuit

Claim 2

A fail-safe electronic comparator circuit comprising, an oscillator circuit having at least two d.c. supply voltages and including a primary winding of a transformer, a tuned circuit having an output and including the secondary winding of said transformer, said tuned circuit tuned to the resonant frequency of said oscillator so that oscillations having said resonant frequency are induced into said tuned circuit when and only when signals applied to both of said at least two d.c. supply voltages are in agreement and no critical component or circuit failure is present in either or both of said oscillator circuit or tuned circuit.

Claim 3

A fail-safe electronic comparator circuit as defined in claim 1, wherein said oscillator circuit is a free-running multivibrator.

Claim 4

A fail-safe electronic comparator circuit as defined in claim 1, wherein said oscillator circuit includes a pair of transistors forming an astable multivibrator.

Claim 5

A fail-safe electronic comparator circuit as defined in claim 1, wherein said oscillator circuit includes a pair of transistors each connected in a common-emitter configuration.

Claim 6

A fail-safe electronic comparator circuit as defined in claim 4, wherein one of said at least two d.c. supply voltages is connected to the base electrodes of said transistors, the collector electrodes of the respective transistors are connected to the ends of said primary winding, and the other of said at least two d.c. supply voltages is connected to the center tap of said primary winding.

Claim 7

A Fail-safe electronic comparator circuit as defined in claim 1, wherein said oscillator circuit includes a pair of transistors forming a collector-coupled multivibrator.

Claim 8

A fail-safe electronic comparator circuit as defined in claim 6, wherein a capacitor is coupled between the respective collector and base electrodes of said transistors.

Claim 9

A transistorized comparator comprising, a free-running multivibrator including a first and a second transistor each having a base, an emitter and a collector electrode, said emitter electrodes of said first and second transistors directly coupled to each other, said base electrodes of said first and second transistors resistively coupled to a first source of d.c. potential, said collector electrodes of said first and second transistors resistively coupled through a primary winding of a transformer to a second source of d.c. potential, the secondary winding of said transformer tuned to the resonant frequency of said multivibrator so that an output signal having a frequency equal to said resonant frequency is available across said secondary winding when said first and second d.c. potentials are substantially equal and in the absence of a critical component or circuit failure in either or both of said free-running multivibrator or said tuned secondary winding.

Claim 10

A transistorized comparator comprising, a free-running multivibrator including a first and a second transistor each having a base, an emitter and a collector electrode, said emitter electrodes of said first and second transistors directly coupled to each other, said base electrodes of said first and second transistors resistively coupled to a first source of d.c. potential, said collector electrodes of said first and second transistors resistively coupled through a primary winding of a transformer to a second source of d.c. potential, the secondary winding of said transformer tuned to the resonant frequency of said multivibrator so that an output signal having a frequency equal to said resonant frequency is available across said secondary winding when said first and second d.c. potentials are substantially equal and in the absence of a critical component or circuit failure in either or both of said free-running multivibrator or said tuned secondary winding.