Abstract: A metal halogen battery construction, with the improved combination comprising, at least one cell having a positive electrode and a negative electrode for contact with aqueous electrolyte containing the material of said metal and halogen, sump means wherein the electrolyte is collected, store means wherein halogen hydrate is formed and stored as part of an aqueous material, circulation means for transmitting electrolyte through the battery, conduit means for transmitting halogen gas formed in the cell to hydrate forming means associated with the store means, fluid jet pump means operative to cause circulation of gases from the sump including hydrogen and halogen to contact a reactor means whereby hydrogen and halogen are combined and returned to the sump, and valve means sensitive to gas pressure in the sump means whereby when sump pressure drops below a desired setting of said valve means, the valve opens and permits halogen gas from the store to be transmitted to the electrolyte circulation means.

Abstract: A device for controlling the rotational speed of a friction welder as a function of the combined length of the pair of parts to be welded, within predetermined tolerances, so as to produce welded pieces of uniform length in spite of minor variations in the lengths of the parts. Logic and sequencing circuitry specially adapted to carry out this function at minimum cost is also described.