HISTORY
Chronically short of funds, Baird had been trying to get industrial interest from the radio manufacturers and from the BBC ever since he had started serious experimental work in television in early 1923. These efforts had mixed results, but his broader public approaches bore fruit, despite the fact that his invention was still under development. The Selfridges demonstrations brought the added bonus of a fee which helped Baird’s research financially, as he had been under pressure from his chief financier, cinema owner Wilfred Day, to provide an immediate return on investment.
megohms. The current from the cell is taken through an amplifier and amplified sufficiently to enable it to actuate the loud speaker. From the label (3) in the G.H. Davis drawing below, it is suggested that the cell that would be used at Selfridges was not Case’s Thalofide cell, but one which Baird described for Wireless World as ‘neither a photo-electric nor a selenium cell, but a colloidal (fluid) cell of my own invention, of which I hope to give particulars at a later date’. Such a cell is described in a letter from Baird to Day dated 13 October 1924. Long suggests that this cell may have been
two accounts of it—by the later military wireless expert Dr. Alan Butement, and by A.F. Birch [an engineer who worked with Baird from 1928–30].
In his Wireless World article, Elwell wrote:
The cell we use, and which must be used for talking motion pictures, must be instantaneous in its action, and the photo- electric cell invented by Mr. T.W. Case, and known as the Thalofide cell, is used. It consists of a deposit of thallium and sulphur on a quartz disc, 3/4 in. diameter. It is very sensitive in action but of very high resistance, sometimes as much as 500
Baird’s Laboratory at 22 Frith Street
In November 1924, Baird returned to London from Hastings where he had spent the past two years recovering from a serious illness, and where he had done most of his television experiments. His decision to return was due to a combination of problems with his Hastings landlord, Mr. Tree, and the desire of his officious business partner, Will Day, that Baird work nearby. Day was based in London at 19 Lisle Street, Soho. He arranged premises for Baird to use as his makeshift laboratory—the attic rooms of 22 Frith Street, also in Soho. The television apparatus that Baird was using at this time was electro-mechanical. The camera consisted of a rotating transmitter disc, fitted with sixteen glass lenses to collect the light. The receiver was based on a second disc of similar size, punched with sixteen rectangular holes. This spinning disc acted to rapidly align the variations of light with their position to form a coherent picture for the human eye. In early 1925, this apparatus was described in detail by Baird himself in an article in Wireless World.2 Chris Long notes that this article is in the same issue as Cyril Elwell’s article on the reproduction of optical film soundtracks in the DeForest Phonofilm system. Long writes: The DeForest London studio at Clapham used Theodore Case’s ‘Thalofide’ photoresistive cell, far faster in response than any earlier photoresistive cell, and I believe it was this element that led Baird, in October 1925, to attain the first practical achievement of ‘true television’—the reproduction of a recognisable human face, in movement, by reflected light. Since reading these two articles I’ve checked for any mention of Baird’s presence at DeForest’s Clapham studio, and now have
G.H. Davis’ drawings of Baird’s apparatus in early 1925. Image source: The Graphic (28 February 1925)
SEPTEMBER 2025 Volume 47 No.3
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