Glass break detector having reduced susceptibility to false alarms

A detector system for detecting penetration of a contact-sensitive surface, comprising:

• a transducer for detecting, and developing a motion signal indicative of, a wave of changing amplitude produced in response to motion resulting from a contact force applied to the surface;
• a peak analyzer responsive to the motion signal for determining amplitude peaks in the motion signal, the peak analyzer providing a valid signal whenever the absolute value of a first amplitude peak is greater than the absolute value of a second amplitude peak, the first and second amplitude peaks being consecutive amplitude peaks of the motion signal that are of opposite polarity relative to a reference level and the first amplitude peak reaching a predetermined threshold, or whenever the second amplitude peak reaches a negative value that equals a predetermined negative threshold;
• and
• an alarm responsive to the valid signal.

A detector system for detecting penetration of a contact-sensitive surface, comprising:

• a transducer for detecting, and developing a motion signal indicative of, a wave of changing amplitude produced in response to motion resulting from a contact force applied to the surface;
• a low frequency detector comprising a low frequency filter responsive to the motion signal for generating a low frequency motion signal and a peak analyzer responsive to the low frequency motion signal for determining amplitude peaks in the low frequency motion signal, the peak analyzer providing a signal whenever the absolute value of a first amplitude peak is greater than the absolute value of a second amplitude peak, the first and second amplitude peaks being consecutive amplitude peaks of the low frequency motion signal that are of opposite polarity relative to a reference level and the first amplitude peak reaching a predetermined threshold;
• and
• an alarm responsive to the signal provided by the peak analyzer.

A detector system for detecting penetration of a contact-sensitive surface, comprising:

• a transducer for detecting, and developing a motion signal indicative of, a wave of changing amplitude produced in response to motion resulting from a contact force applied to the surface;
• a low frequency detector comprising a low frequency filter responsive to the motion signal for generating a low frequency motion signal and a peak analyzer responsive to the low frequency motion signal for determining amplitude peaks in the low frequency motion signal, the peak analyzer providing a signal whenever the absolute value of a first amplitude peak is greater than the absolute value of a second amplitude peak, the first and second amplitude peaks being sequential amplitude peaks of the low frequency motion signal and of opposite polarity relative to a reference level;
• an alarm responsive to the signal provided by the peak analyzer;
• and
• the low frequency detector further includes low frequency circuitry characterized by a low frequency saturation amplitude, the peak analyzer providing a signal to enable the alarm whenever the second amplitude peak reaches a low frequency saturation amplitude of negative value.

A detector system for detecting penetration of a contact-sensitive surface, comprising:

• a transducer for detecting, and developing a motion signal indicative of, a wave of changing amplitude produced in response to motion resulting from a contact force applied to the surface;
• a low frequency detector comprising a low frequency filter responsive to the motion signal for generating a low frequency motion signal and a peak analyzer responsive to the low frequency motion signal for determining amplitude peaks in the low frequency motion signal, the peak analyzer providing a signal whenever the absolute value of a first amplitude peak is greater than the absolute value of a second amplitude peak, the first and second amplitude peaks being sequential amplitude peaks of the low frequency motion signal and of opposite polarity relative to a reference level;
• an alarm responsive to the signal provided by the peak analyzer;
• a mid-frequency bandpass filter having a center frequency that exceeds frequencies passed by the low frequency filter, the mid-frequency bandpass filter detecting a mid-frequency acoustic wave characteristic of breaking glass from the motion signal;
• and
• a logic circuit for providing a signal to which the alarm is responsive whenever the low frequency detector detects during a predetermined time period that the absolute value of the first amplitude peak is greater than the absolute value of the second amplitude peak, the detecting of the mid-frequency acoustic wave initiating the predetermined time period.