Abstract: A speaking and hearing system for respirators, where the apparatus wearer is connected to a respiratory gas supply independent of the ambient air. A suppression, independent of acoustic signals, of the breathing noises of the apparatus wearer is provided by a switch device located in the respiratory gas line which reacts to the respiratory gas stream for the suppression of the breathing noises.

Abstract: The respirator for use in pressure chambers serves to ventilate patients in therapeutic areas or in diver pressure chambers at diverse pressures. All its operations are effected pneumatically. The selected (a) ventilating volume supplied to the patient must remain constant (in operating liters) and the selected (b) breathing rate must be maintained. For meeting condition (a), the respirator contains a known pressure ratio regulator working on the double-diaphragm principle, and for meeting condition (b) it contains a frequency stabilizer. The frequency stabilizer contains in a housing a stepped piston moved by the chamber pressure against a spring, forming two volumes. The ratio of the free piston surfaces to each other determines the breathing time ratio. The volumes, adjusted by the chamber pressure over the height, determine the breathing rate together with the gas amount/time unit set by a precision adjusting valve.