Acoustic alarm detection system for telephone activation

• US 4,897,862 A
• Filed: 05/27/1988
• Issued: 01/30/1990
• Est. Priority Date: 05/27/1988
• Status: Expired due to Term

• Current Assignee: NEC Technologies Incorporated
• Original Assignee: NEC Corporation
• Inventors: Nishihara, Kaneyuki, Tomimori, Akinobu, Rittmueller, Philip H.
• Primary Examiner(s): George, Keith E.
• Application Number:
  US07/199,481
• Time in Patent Office: 613 Days
• Field of Search: 379/39-43, 379/102, 379/105, 340/531, 340/540
• US Class Current: 379/40
• CPC Class Codes: H04M 11/04 with alarm systems, e.g. fire, police or burglar alarm systems

Abstract

An electronic device for generating an activation signal in response to detection of an acoustic signal having parameters within respective predetermined ranges, and then automatically dialing a prestored telephone number and transmitting a prerecorded message over the telephone line in response to the activation signal. The device includes a transducer for transducing an acoustic signal into an electrical signal; a detector for outputting an activation signal in response to detection of an acoustic signal having parameters within respective predetermined ranges; and a telephone module for automatically dialing a prestored number and transmitting a prerecorded message in response to the activation signal. The detected parameters include the amplitude of the acoustic signal, the frequency of the acoustic signal, the duration of each burst of the acoustic signal, and the duration of each interval between successive bursts of the acoustic signal.

Claims

1. An electronic device for generating an activation signal in response to detection of an acoustic signal having parameters within predetermined ranges, comprising:

converting means for producing square wave pulses having durations which correspond to durations of bursts of an acoustic signal having a frequency within a predetermined passband;

detection means coupled to said converting means for outputting a reset counter signal in response to each detection of a pulse having a duration outside of a first predetermined range a in response to each detection of a pulse interval between successive pulses having a duration outside of a second predetermined range, and outputting an increment counter signal in response to each detection of a trailing edge of a pulse; and

counting means for incrementing a count by unity in response to each detection of an increment counter signal and outputting an activation signal in response to a detection of a predetermined number of successive increment counter signals, said count being restarted in response to each detection of a reset counter signal.

2. An electronic device for generating an activation signal in response to detection of an acoustic signal having parameters within predetermined ranges, comprising:

means for transducing an acoustic signal into an electrical signal;

preamplifying means coupled to said transducing means for preamplifying the electrical signal;

means coupled to said preamplifying means for amplifying the preamplified electrical signal with a variable gain;

high pass filter means coupled to said amplifying means for removing signal components having a frequency less than a predetermined lower threshold frequency;

low pass filter means coupled to said high pass filter means for removing signal components having a frequency greater than a predetermined upper threshold frequency;

rectifying means coupled to said low pass filter means for performing half-wave rectification of an amplified and filtered signal outputted by said low pass filter means;

converting means coupled to said rectifying means for producing a square wave pulse train having pulse lengths and intervals between pulses corresponding to bursts and burst intervals outputted by said half-wave rectifying means;

detection means coupled to said converting means for outputting a reset counter signal in response to each detection of a pulse having a duration outside of a first predetermined range and in response to each detection of a pulse interval between successive pulses having a duration outside of a second predetermined range, and outputting an increment counter signal in response to each detection of a trailing edge of a pulse; and

counting means for incrementing a count by unity in response to each detection of an increment counter signal and outputting an activation signal in response to a detection of a predetermined number of successive crement counter signals, said count being restarted in response to each detection of a reset counter signal.

3. The electric device as defined in claim 2, wherein said detection means comprises a plurality of monostable multivibrators connected in parallel and logic circuitry for outputting said reset counter signal.

4. An electronic device for generating an activation signal in response to detection of an acoustic signal having parameters, including burst durations and intervals between bursts, within predetermined ranges, comprising;

means for transducing an acoustic signal into an electrical signal; and

means for outputting an activation signal in response to detection of a predetermined number of bursts of an acoustic signal having said parameters within said respective predetermined ranges, said activation signal for coupling to a means for automatically dialing a prestored number and transmitting a prerecorded message in response to said activation signal,

wherein said parameters comprise the amplitude of said acoustic signal, the frequency of said acoustic signal, the duration of each burst of said acoustic signal, and the duration of each interval between successive bursts of said acoustic signal.