IEEE MILESTONE IN ELECTRICAL ENGINEERING AND COMPUTING
Invention of Stereo Sound Reproduction, 1931
Alan Dower Blumlein filed a patent for a two-channel audio system called "stereo" on 14 December 1931. It included a "shuffling" circuit to preserve directional sound, an orthogonal "Blumlein Pair" of velocity microphones, the recording of two orthogonal channels in a single groove, stereo disc-cutting head, and hybrid transformer to mix directional signals. Blumlein brought his equipment to Abbey Road Studios in 1934 and recorded the London Philharmonic Orchestra.
April 2015
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The sign is on the wall of Abbey Road Studios (best known for the recordings of the Beetles’ songs).
The plaque commemorates the inventor of the stereo technology, Alan Blumlein, a British electrical engineer. The engineer worked for the Gramophone company that set up these studios.
The plaque is given by IEEE - Institute of Electrical and Electronics Engineers, the largest association of electronics and computer professionals.

The studios were photographed on the same day Click for a larger image

Next to this plaque, there is also a commemorative plaque for the composer Edward Elgar whose recordings he made inaugurated the studios Click for sign's details