Automatic detection of microphone sabotage in a security system device

1. A method of automatically detecting sabotage of an audio transducer in a security system device comprising the steps of:

a. generating an electrical signal from an audio transducer;

b. analyzing the electrical signal to determine if the electrical signal comprises a predetermined sabotage characteristic; and

c. if the electrical signal comprises a predetermined sabotage characteristic, then transmitting an alarm device trouble signal.

2. The method of claim 1 further comprising the steps of

d. if the electrical signal does not comprise a predetermined sabotage characteristic, then

i. analyzing the electrical signal to determine if the electrical signal comprises a predetermined alarm characteristic; and

ii. if the electrical signal comprises a predetermined alarm characteristic, then transmitting an alarm signal.

3. The method of claim 1 wherein the step of analyzing the electrical signal to determine if the electrical signal comprises a predetermined sabotage characteristic comprises the steps of:

i. digitizing the electrical signal to generate a digitized signal, and

ii. processing the digitized signal to determine if the electrical signal comprises a predetermined sabotage characteristic.

4. The method of claim 1 wherein the step of analyzing the electrical signal to determine if the electrical signal comprises a predetermined sabotage characteristic comprises the steps of:

i. determining the presence of a first voltage transition of the electrical signal in the positive direction exceeding a first predetermined voltage threshold and lasting for a first predetermined period of time; and

ii. determining the presence of a second voltage transition of the electrical signal in the negative direction exceeding a second predetermined threshold and lasting for a second predetermined period of time;

wherein the second voltage transition occurs within a third predetermined time after the first voltage transition.

5. The method of claim 1 wherein the step of analyzing the electrical signal to determine if the electrical signal comprises a predetermined sabotage characteristic comprises the steps of:

i. determining the presence of a first voltage transition of the electrical signal in the negative direction exceeding a first predetermined voltage threshold and lasting for a first predetermined period of time; and

ii. determining the presence of a second voltage transition of the electrical signal in the positive direction exceeding a second predetermined threshold and lasting for a second predetermined period of time;

wherein the second voltage transition occurs within a third predetermined time after the first voltage transition.

6. A security system device comprising:

a. an audio transducer adapted to generate an electrical signal as a result of sensing sound;

b. a sabotage analysis processing circuit adapted to analyze the electrical signal to determine if the electrical signal comprises a predetermined sabotage characteristic and then generate an alarm device trouble signal; and

c. transmitting circuitry adapted to transmit the alarm device trouble signal generated by the sabotage analysis processing circuit.

7. The device of claim 6 further comprising:

d. an alarm signal analysis processing circuit adapted to analyze the electrical signal to determine if the electrical signal comprises a predetermined alarm characteristic.

8. The device of claim 6 wherein the sabotage analysis processing circuit comprises:

i. digitizing circuitry for digitizing the electrical signal to generate a digitized signal, and

ii. processing circuitry adapted to process the digitized signal and determine if the electrical signal comprises a predetermined sabotage characteristic.

9. The device of claim 6 wherein the sabotage analysis processing circuit comprises:

i. a high level threshold detector circuit and a positive phase detector circuit, adapted to determine the presence of a first voltage transition of the electrical signal in the positive direction exceeding a first predetermined voltage threshold;

ii. a positive duration timer circuit adapted to determine if the first voltage transition lasts for a first predetermined period of time;

iii. a low level threshold detector circuit and a negative phase detector circuit, adapted to determine the presence of a second voltage transition of the electrical signal in the negative direction exceeding a second predetermined threshold;

iv. a negative duration timer circuit adapted to determine if the second voltage transition lasts for a second predetermined period of time; and

v. a microphone sabotage processing circuit adapted to determine if the second voltage transition occurs within a third predetermined time after the first voltage transition.

10. The device of claim 6 wherein the sabotage analysis processing circuit comprises:

i. a low level threshold detector circuit and a negative phase detector circuit, adapted to determine the presence of a first voltage transition of the electrical signal in the negative direction exceeding a first predetermined voltage threshold;

ii. a negative duration timer circuit adapted to determine if the first voltage transition lasts for a first predetermined period of time;

iii. a high level threshold detector circuit and a positive phase detector circuit, adapted to determine the presence of a second voltage transition of the electrical signal in the positive direction exceeding a second predetermined threshold;

iv. a positive duration timer circuit adapted to determine if the second voltage transition lasts for a second predetermined period of time; and

v. a microphone sabotage processing circuit adapted to determine if the second voltage transition occurs within a third predetermined time after the first voltage transition.