Donald Earle Combs: Pulse-width modulated DC to DC converter with zero percent duty cycle capability. Bell Telephone Laboratories, R J Guenther et al, October 31, 1972: US3701937 (52 worldwide citation)

A pulse-width modulated DC to DC converter is enabled to operate into short circuits and limit the current output by having the capability of operating at zero percent duty cycle. The regulation feedback loop utilizes a light-emitting diode and phototransistor optical arrangement to permit isolation ...

Raymond Charles Pitetti, Walter Worobey: Thin film capacitor including an aluminum underlay. Bell Telephone Laboratories, R J Guenther et al, June 20, 1972: US3671823 (2 worldwide citation)

The use of an aluminum film beneath the tantalum anode of a tantalum thin film capacitor results in a significant enhancement in the frequency response of the capacitor and a lower dissipation factor at frequencies above 10 kilohertz than normally evidenced by devices not including the aluminum film ...

Earl Truman Ratliff, Paul William Renaut: Reed switch having contacts plated with a thin silver layer. Bell Telephone Laboratories, R J Guenther et al, September 5, 1972: US3689722 (1 worldwide citation)

A sealed contact dry reed switch in which nickel-iron reed contacts are held in a glass envelope by seals and in which the surfaces of the reed contacts, including those portions under the seals, are covered with a thin layer of silver.