A hearing aid of 1952 standing upright on a counter covered with green felt in the fitting room of a hearing aid shop in New York State, a flat case of matt silvery grey metal with rounded corners eight centimetres high, six centimetres wide and one centimetre thick, the upper half of its front a fine grille of horizontal slots, the lower half smooth, a small knurled wheel at the upper right, a thin cord leading to a small beige earpiece beside it, an open case with a velvet bed, a hand in a grey wool sleeve holding the case by its edge, wooden shelves soft behind, winter daylight from the left.
What it was used for
The Sonotone 1010 hearing aid reached the market in December 1952 at $229.50 and is, per the Computer History Museum, the first commercial product to use a transistor. It was a hybrid: two subminiature vacuum tubes and 1 transistor, supplied by the Germanium Products Corporation. The transistor sat not where it would be heard but where it would save; the museum gives its purpose as longer battery life without sacrificing sound quality. Raytheon developed the CK718 exclusively for hearing aids and sold it only to hearing aid companies; by late 1952 it was making thousands every week, according to the museum. In 1953 Maico brought out an aid using 3 of them and no tubes.
What was new
What was characteristic was not the circuit but the running cost. The Computer History Museum calls the CK718 the first commercial high-volume alloy junction transistors on the market, and gives as the reason for the switch that Raytheon's own point-contact types were too noisy and too fragile for hearing aids. The result was a price collapse in two directions: in the account given by PBS and AIP, battery costs fell from nearly $100 to about $10, and Acousticon brought out a single-transistor aid at $74.50, a third of the Sonotone price. By 1954, per the museum, almost all hearing aids were transistorised, 97 per cent; Raytheon was the largest transistor maker from 1952 to 1955.
What the sources leave open: PBS and AIP give honouring Alexander Graham Bell as the motive for the royalty-free licence. No source opened gives weight, dimensions, battery type or sales figures for the Sonotone 1010; hearingaidmuseum.com was unreachable.