Abstract: A self-contained portable personal breathing apparatus that has a casing housing a canister containing an oxygen evolving chemical. The casing is disposed inside a cover which is disposed inside a bag. The cover and the casing form a thermal insulating pocket between them, and with the cover material and the casing material, also made of thermally insulating material, a triple layer of thermal insulation is formed around the canister to protect oxygen produced therein from the heat of reaction of the chemical in the canister. A heat exchanger is situated atop the canister to further cool oxygen before inhalation, and breathing tube extends from the bag to the user for channeling exhaled breath and oxygen.

Abstract: An electronic circuit for processing measured values obtained from a vortex sequence produced by a Karman vortex path, wherein the ultrasonically sensed signals are processed both digitally in a first circuit branch for a computer and analogously in a second circuit branch for the connection of a two-channel continuous recorder. An adjustable frequency transforming arrangement is serially connected in the computer branch for balancing the circuit, and an additional frequency-voltage converter and and integrator are serially connected in the recorder branch along with a control logic circuit inserted between the two branches for starting the recorder after activation of the computer only when signals which can be evaluated are present.