Abstract: Method and apparatus for frequency domain modulation optical fiber communication particularly useful for digital and analog signal transmission comprising, in the order recited, a plurality of parallel-connected signal input units each incorporating individual laser sources provided with means modulating the output radiations of said laser sources responsive to individual signal inputs, thereby establishing, for each signal input, an individual optical information wave train, a collimating lens, an acousto-optical modulator means introducing a sub-carrier signal developing a beat frequency with said optical information wave train, an optical fiber coupler transmitting the resulting signal through an optical fiber to a common square law detector and an information receiver isolating a preselected individual signal input according to its associated individual sub-carrier frequency, said individual sub-carrier frequencies being spaced one from another by an interval forestalling interference in the reception of

Abstract: An improved photovoltaic cell, and method for its manufacture, comprising front and back electrically conductive layers between which is sandwiched a primary light-absorbing layer of amorphous semiconducting material displaying low photogenerated carrier mobility below about 50 cm.sup.2 /V second, the constitution of which primary layer is fabricated to provide an affinity gradient reducing back-diffusion of a preselected species of photogenerated carrier (electrons or holes) to thereby forestall non-productive recombination with carriers of opposite type.

Abstract: An electrical recharging apparatus for hearing aid batteries utilizing C or D dry cells as the charging source, and a solid state regulating circuit connected in shunt with the battery to be charged which maintains the charging current at a safe recharge rate below the level where the battery to be charged will be damaged and the recharge voltage within relatively narrow limits regardless of load, line or service temperature variations.