Abstract: A respirator system includes a facepiece, a communication system and a control system in operative connection with the communication system. The control system is adapted to control voice transmittal via the communication system based at least in part upon measurement of a variable other than sound. The variable is related to speech of a user of the facepiece. The variable may, for example, be related to respiration of the user.

Abstract: The present invention provides a system and a method for controlling and detecting faults in a pump system for use in a gas detection device. The system comprises a power source and a switch in operative or electrical connection with the power source. The system further comprises a pump motor in operative connection with the switch such that the pump motor receives energy from the power source when the switch in a first state, and the pump motor does not receive energy from the power source when the switch in a second state. The system preferably also comprises regeneration circuitry in operative connection with the pump motor. The regeneration circuitry operates to redirect energy produced from momentum of the pump motor while the switch is in the second state back to the pump motor. Transmitting circuitry is preferably provided to transmit a motor signal proportional to the speed of the pump motor during the second state of the switch.

Abstract: The present invention relates to a programmable current or voltage sensing circuit for use in measuring concentration levels of combustible gases. Generally, the present invention provides an electrical apparatus for detecting the concentration level of a combustible gas comprising a pair of sensor elements each having an electrical output which is compared to the other for measuring the amount of the gas undergoing combustion. The apparatus also generally comprises a first pair of electrical circuits each connected to one sensor element for controlling the amount of electrical current or voltage at that element, a second electrical circuit connected to both elements for comparing the electrical outputs of the sensor elements to measure the amount of gas undergoing combustion, and a third electrical circuit having a reference output signal for individually controlling the amount of electrical current or voltage generated by each of the first electrical circuits.