Question: Elmer T. Cunningham infringed on the vacuum tube patent of the British electrical engineer and physicist, born on what day?
Sentence (from "Grid-leak detector"): A grid-leak detector is a thermionic valve (UK, Australia, NZ etc.), or vacuum tube (USA), circuit used in older vacuum tube AM radio receivers, which served as a combination amplifier and detector (rectifier) to extract the audio signal from the modulated radio frequency signal.
Relevant evidence: No