Patent ID: 7821418

Claim:
A safety system comprising: an elongate signal carrying device including a wave carrying hollow tube with a first end and a second end and a fluid therein, at least a part of the hollow tube being manipulable at a manipulation point to generate a measurable non-electric acoustic signal that can be carried by the hollow tube; an acoustic microphone detector for detecting the non-electric acoustic signal, the acoustic microphone detector outputting a detector output signal representing the non-electric acoustic signal; a detector processing device that processes the detector output signal to detect a quiescent level of the detector output signal and to detect deviations from the quiescent level indicative of positive or negative changes in pressure in the fluid of the hollow tube, the detector processing device including a low pass filter that filters the detector output signal to remove a background non-electric signal therefrom, the detector processing device outputting a detector processing device output signal; and an output device operatively connected to the detector processing device for causing an audible alarm signal, a visible alarm signal or an electric signal to be output in response to the detector processing device output signal.