Telechrome

One of the sides was covered in cyan phosphor and the other red-orange, producing a limited color gamut, but well suited to displaying skin tones.

Telechrome was selected as the basis for a UK-wide television standard by a committee in 1944, but the difficult task of converting the two-color system to three-color RGB was still under way when Baird died in 1946.

The introduction of the shadow mask design by RCA produced a workable solution for color television, albeit one with considerably less image brightness.

Baird performed one of the earliest public demonstrations of color television system on 3 July 1928 using an all-mechanical system with three Nipkow disk scanners synchronized with a single disk on the receiving end and three colored lights that were turned on and off in synchronicity with the broadcaster.

The same basic system was used on 4 February 1938 to create the first color broadcast transmissions from The Crystal Palace to the Dominion Theatre in London.

This design was physically very long, leading to deep receiver chassis, but later versions folded the optical path using mirrors to produce a somewhat more practical system.

Transmitting such a signal could be accomplished by using three camera tubes, each with a color filter in front of them, using mirrors or prisms to aim at the same scene through a single lens.

The system used in the cameras, with three separate tubes combined together optically, was not practical due to the cost of a receiver set with three CRTs as well as the unwieldily chassis needed to contain them.

A number of experiments were carried out using more conventional tubes and then filtering them, but the low output of the CRTs produced very dim images that were dismissed as impractical.

In 1941 Baird converted a teapot projector to produce a two-color image by placing filters in front of the two tubes and projecting them onto a smaller screen to improve the effective intensity.

Lens systems focused on the display were positioned to see only the top or bottom image, passed them through filters, and then recombined them on a screen.

[8] The earliest test models used screens only a few inches across and had the guns arranged almost at right angles to it, making for a very large tube.

[8] Later models were built inside very large Hackbridge-Hewittic (H-H) vacuum tubes, which the company originally designed for use as high-power rectifiers in power supplies.

Similar designs were attempted by a number of researchers, the best known was the Geer tube that used pyramid-shaped patterns with three guns arranged around the back.

[15] There is no documentary evidence that a successful version of the three-gun Telechrome tube was ever built, although images of Baird holding what is claimed to be a prototype are widely duplicated.

The image shows a three-neck tube, but the third neck is the original Hewittic port, now used to hold the internal screen.

[14] They went on to note: Apart from the coated mica screen, we do not think any new invention has been demonstrated, and we consider that development on a scale far beyond the capabilities of Mr. Baird's present organisation is necessary for successful results.

[14] In 1943, with the war clearly turning in the Allies favor, Winston Churchill formed a series of committees to consider post-war redevelopment.

[17] The Committee met numerous times during the next year, and asked Baird to prepare a number of papers on the topic of post-war broadcasting.

Among his suggestions, he stated that the BBC's monopoly should be ended and independent broadcasters should be licensed, which was delivered along with a request to start such a service.

[17] Baird was called to a 29 February 1944 meeting of Cable and Wireless (C&W) to discuss the formation of a color television studio.

This combined a 27 inches (690 mm) black and white television, a radio receiver and a record-changing record player in a single large cabinet.

[21] Many years later, former Baird employee Edward Anderson was quoted as saying that they "had the equivalent of the Sony Trinitron tube on the drawing board".

[22] This has been used by a number of non-technical authors to suggest that the Trinitron is in some way technically related to the Telechrome in spite of the two systems having nothing in common.