A system for sensing respiratory pressure includes a portable pressure transducer configured to be carried by or proximate to a respiratory conduit, such as a breathing circuit or a nasal canula. A rubber tie extends through the central opening and a retaining wire extends through a transverse aperture in the tie. The level shifter detects when the VDD power supply is on and sets an enable signal to the status circuit. A charge time difference of any two cell strings in the battery is used to determine the cell imbalance condition by comparing with a predetermined acceptable charge time difference for the cell strings. In response to the locate signal, the remote control provides audio and visual signals to assist a user in finding the remote control unit.