Abstract: An integrated, improved, fully redundant mixed gas breathing apparatus gas routing manifold permits inhalation and exhalation lines from both mouthpieces of a closed circuit breathing system and an automatic gas addition system to be cross routed to the opposite system's CO.sub.2 removing and gas control system.

Abstract: A mixed gas breathing apparatus reversibly switchable between open circuit and closed circuit systems. Three embodiments show three different levels of redundancy: nonredundant, bi-linear redundant and fully redundant. The counterlung minimizes the static lung loading and thus decreases breathing resistance. Manual control system is readily accessible and allows control of addition of the breathing gases.

Abstract: A waterproof digital lap counter automatically counting and indicating the number of laps traversed by a swimmer having the lap counter attached to a hand or foot comprises a LCD array including a digital counter, driver and LCD embedded within a sealed inner housing which is slidably and nonrotatably supported in an outer housing. Counting and indication of laps traversed occurs automatically and is triggered by abutment of the lap counter against the side of the swimming pool during the swimming stroke or flip turn of the swimmer. Abutment of the lap counter against the side of the pool momentarily closes a switch which sends an input signal to the LCD array representative of a lap traversed. The LCD array counts and provides a visible indication of the number of input signals received which corresponds to the total number of laps traversed.