Signal monitoring system

A generator brush monitor adapted to provide a signal upon the occurrence of generator brush arcing voltages exceeding a predetermined value and comprising:

• a. means receiving a voltage signal including high frequency information signals representative of generator brush arcing and low frequency signals representative of the generator voltage and various harmonics thereof as well as possible recurrent high frequency noise spikes in the same frequency band as said information signals;
• b. filter means for filtering said low frequency signals from said received voltage signal;
• c. clipping means for removing excess positive-going and negative-going peaks of said information signals;
• d. means for adjusting the level of said information signals to which said monitor is responsive;
• e. gating means receiving the filtered and clipped information signals and adapted to pass said information signals unless said gating means is in receipt of a disabling signal, but only for substantially the duration of said disabling signal and its ringing;
• f. means responsive to the output of said gating means to amplify and integrate said gated signal;
• g. means responsive to said amplified and gated information signal for comparing the same with an adjustable reference voltage for producing an alarm signal when said information signal exceeds the adjusted value of said reference voltage;
• h. means coupled to said clipping means for providing a disable pulse and to maintain the same substantially so long as a noise signal and its ringing is present in said input voltage signal and to supply said disable pulse to said gating means;
• i. said gating means being further adapted to gate said information signal so long as said disable pulse is input thereto but only substantially for such period so that said monitor is operative to receive and act in response to said information signals except when it is in receipt of a noise signal in the same frequency band as said information signals.