Fail-safe constant amplitude signal generator

A constant amplitude signal generator which is capable of producing an a.c. output signal when no critical circuit failure is present and which is incapable of producing an a.c. output signal when a critical circuit failure is present comprising, a source of d.c. biasing potential, a shunt regulator connected across said source of d.c. biasing potential, said shunt regulator including a pair of series connected resistors connected in series with a Zener diode having an anode and cathode, an oscillator having a transistor including a base, an emitter and a collector electrode, a voltage divider network having a first and a second resistor connected between the anode of said Zener diode and the junction of said pair of series connected resistors, a resonant tank circuit including an inductor and capacitor electrically connected to said Zener diode, said inductor forming the primary winding of a transformer which includes a secondary feedback winding and a secondary output winding, said secondary feedback winding connected between the base electrode of said transistor and the junction of said first and second resistors of said voltage divider, said collector electrode of said transistor coupled to the junction of said inductor and said capacitor and said emitter electrode of said transistor resistively coupled to said source of d.c. biasing potential.