Hearing aid battery recharging apparatus

Claim 1

An electrical recharging apparatus for hearing aid batteries of the silver oxide and mercurous oxide types comprising, in electrical circuit in the order recited: (a) a dry cell charging source supplying, across its output terminals, a charging potential of, nominally, 3 volts, (b) an "ON-OFF" double pole single throw switch having switching contacts interposed in series with each of said charging source output terminals, (c) a preselected charging current-controlling resistor, (d) hearing aid battery charging contacts connected at corresponding polarity sides with said output terminals of said charging source and with said hearing aid battery to be charged via said preselected charging current-controlling resistor and said "ON-OFF" switch, and (e) a voltage regulating circuit connected in shunt with said battery charging contacts past said "ON-OFF" switch comprising a first transistor connected via its collector and emitter elements, respectively, in series relationship between said charging source and one charging contact for said hearing aid battery in a polarity sense maintaining charging current flow through the collector-emitter pair of said first transistor, a preselected biasing resistor, a second transistor connected with its collector element in circuit with the base element of said first transistor and with the collector element of said first transistor via said preselected biasing resistor which, in conjunction with said second transistor, limits the base-emitter current of said first transistor, a potentiometer, the emitter element of said second transistor connected to the appropriate polarity side of said charging source and the base element of said second transistor connected to the tap of said potentiometer which is connected from emitter element to emitter element of said transistors in shunt across said battery charging contacts.