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1922. Washington, D.C. "Radio at District jail." Programming for a captive audience. Harris & Ewing Collection glass negative. View full size.
On his hat, the symbol for mu is the giveaway for Doctor Mu.
That old advertisement is quite cool.
In vacuum tubes the amplification factor (gain) of a tube was measured in MU . High gain = high mu
At the bottom it says "The Sine of GREBE RADIO The Right Kind".. a play on the word SIGN but referring to the RF sine wave that an AM radio received. The sine wave contained the high frequency RF component (GREBE RADIO) and the low frequency audio component (the big sideways "S" underlining the words.
Well played, Dr. MU ... well played !!
The famous Grebe CR-9 radio receiver from 1921.
if they're playing an early recording of Jailhouse Rock
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