frequency, and so greatly simplifies the design of the amplifier circuits." http://www.radiomuseum.org/forum/single_pentode_wien_bridge_oscillator.html http://www.americanradiohistory.com/Archive-Bell-Laboratories-Record/40s/Bell-Laboratories-Record-1945-12.pdf has Black bio; "Stabilized feedback amplifier" won prize in 1934. Later (31 December 1940) Meacham patent about multi-frequency bridge-stabilized oscillators using series resonant circuits. Electronic oscillators Analog circuits Electronic test equipment