Monitor circuit

Claim 2

A circuit for monitoring the operation of a telephone ringing generator circuit that generates ringing signals having periodic ringing bursts, said monitor circuit comprising: a bistable circuit having a normal state and an alarm state; circuit means for receiving the ringing signals and developing signal pulses the duration of which is a function of the amplitude and duration of said ringing bursts, and having a repetition rate corresponding to the repetition rate of said ringing bursts, and a time delay circuit developed between said bistable circuit and said circuit means for switching said bistable circuit into said alarm state if the period between said signal pulseS is longer than the time delay period of said time delay circuit.

Claim 3

A monitor circuit as defined in claim 1 wherein: said time delay circuit comprises a unijunction transistor including a charging circuit for triggering said unijunction circuit, and wherein the time duration for charging said charging circuit to trigger said unijunction transistor in absence of a signal pulse defines a minimum acceptable repetition rate for said ringing burst.

Claim 4

A monitor circuit as defined in claim 1 wherein: said bistable circuit comprises a flip-flop circuit, and includes circuit means for switching said flip-flop circuit into said normal state when the monitor circuit is initially energized.

Claim 5

A monitor circuit as defined in claim 1 wherein: said circuit means comprises an integrator circuit coupled to receive said ringing signals and to produce said signal pulses wherein the magnitude and duration of said signal pulses are a function of the amplitude and duration of said ringing burst, and wherein said time delay circuit comprises a charging circuit coupled to an amplitude sensitive trigger circuit to trigger said trigger circuit when said charge reaches a preset amplitude, and a switching circuit coupled between said integrator circuit and said charging circuit to inhibit said charging circuit from charging to the trigger level during the presence of said signal pulses above a preset magnitude.

Claim 6

A monitor circuit as defined in claim 1 wherein: said circuit means includes an integrator circuit coupled to receive the ringing signals to charge capacitive means during the presence of ringing bursts with a potential that is a function of the ringing burst amplitude and duration and discharges the capacitive means in absence of ringing bursts, a biasing circuit for providing a biasing potential, and a switching circuit for producing said signal pulses, the duration of which, is a function of the charge on the capacitor and the magnitude of the biasing potential, and said time delay circuit comprises a charging circuit coupled to an amplitude sensitive trigger circuit to trigger said trigger circuit when said charge reaches a preset amplitude, and circuit means coupling said charging circuit to said switching circuit so that the presence of said signal pulses inhibits said charging circuit from accumulating a charge.

Claim 7

A monitor circuit as defined in claim 5 wherein the time for said charging circuit to reach the trigger amplitude, in absence of signal pulses, is a function of the minimum acceptable repetition rate of said ringing bursts.

Claim 8

A circuit for monitoring the operation of a telephone ringing generator circuit to produce an alarm signal when at least one of the amplitude, duration, and repetition rate of the ringing bursts which comprise the ringing signal falls below a minimum acceptable value, said monitor circuit comprising: a charging circuit; an alarm circuit coupled to said charging circuit for producing continuous alarm signals when the potential stored by said charging circuit reaches a preset magnitude, and circuit means for receiving said ringing signals coupled to said charging circuit to allow said charging circuit to charge to a potential sufficient to switch said alarm circuit when at least one of the amplitude, duration, and repetition rate of said ringing bursts falls below a preset value.

Claim 9

A circuit for monitoring the operation of a telephone ringing generator circuit to produce an alarm signal when at least one of the amplitude, duration, and repetition rate of the ringing bursts which comprise the ringing signal falls below a minimum acceptable value, said monitor circuit comprising: a charging circuit; an alarm circuit coupled to said charging circuit for producing continuous alarm signals when the potential stored by said charging circuit reaches a preset magnitude, and circuit means for receiving said ringing signals coupled to said charging circuit to allow said charging circuit to charge to a potential sufficient to switch said alarm circuit when at least one of the amplitude, duration, and repetition rate of said ringing bursts falls below a preset value.

Claim 10

A circuit for monitoring the operation of a telephone ringing generator circuit that generates ringing signals having periodic ringing bursts comprising: an integrator circuit for developing control signals, the amplitude and duration of which are a function of the amplitude and duration of said ringing bursts and which have a repetition rate corresponding to the repetition rate of said ringing bursts; a charging circuit; a trigger circuit coupled to said charging circuit for producing an output signal when said charging circuit charges to a preset potential; circuit mEans coupling said integrator circuit to said charging circuit to discharge said charging circuit and inhibit said charging circuit from charging to said preset amplitude between ringing bursts while the amplitude, duration, and repetition rate of the ringing bursts are above preset values, and a bistable switching circuit coupled to said trigger circuit so that when said trigger circuit is switched, said bistable circuit is switched to an alarm state.

Claim 11

A circuit for monitoring the operation of a telephone ringing generator circuit that generates ringing signals having periodic ringing bursts comprising: an integrator circuit for developing control signals, the amplitude and duration of which are a function of the amplitude and duration of said ringing bursts and which have a repetition rate corresponding to the repetition rate of said ringing bursts; a charging circuit; a trigger circuit coupled to said charging circuit for producing an output signal when said charging circuit charges to a preset potential; circuit mEans coupling said integrator circuit to said charging circuit to discharge said charging circuit and inhibit said charging circuit from charging to said preset amplitude between ringing bursts while the amplitude, duration, and repetition rate of the ringing bursts are above preset values, and a bistable switching circuit coupled to said trigger circuit so that when said trigger circuit is switched, said bistable circuit is switched to an alarm state.