Television

In 1931 Columbia merged with The Gra­mophone Company (HMV) to form Electric­al and Musical Industries Ltd, now Thorn-EMI. It was this new company that developed the 405-line electronic television system which became the standard British format and which remained in use until 1985. The format for the picture signal became a world standard, altered only to include colour and stereo sound. Blumlein was the principal architect of the waveform and some people call it the Blumlein signal.

The development of television at EMI was a team effort and involved names which have become legendary in British television: Isaac Shoenberg, J.D. McGee, E.L.C. White and others with of course Blumlein. Blumlein was a major contributor to the circuit design and he had a hand in other areas including the Emitron camera tube, transmission cables and aerials. Among the circuits he invented or developed were a novel sawtooth generator for scanning, negative feedback circuits and the cathode-follower. He also invented and named the long-tailed pair circuit which was devised to reduce interference at the receiving end of a new video cable laid to Alexandra Palace.

Radar

When the Second World War began engineers in Britain already had considerable experience of radar development, all of it conducted in secret. EMI had barely touched radar work but the television team had the expertise for dealing with pulse techniques. So it was that the team which developed television turned to radar. Blumlein, White and others were soon at work on 200MHz airborn-interception radar. This was followed by a model which searched for and locked on to an echo, thus allowing a fighter pilot to operate without a radar operator. The radar work involved a range of activities including frequency-shift keying, klystrons and magnetrons, anti-jamming circuits and so on.

It was during this radar work that Blumlein designed a ramp waveform or timebase generator more linear than any previously achieved. To do it he made use of a usually unwelcome effect in a triode valve circuit first noticed by John M. Miller and subsequently called the Miller effect. Blumlein called the circuit the Miller integrator, a name which stuck and kept his own name out of the electronics text books.

The next major work was a plan-position radar which gave a picture of the ground below the aircraft, so permitting very accurate navigation. It was code-named H₂S and was developed jointly by EMI and TRE (later the Royal Radar Establishment).

With two EMI colleagues and a good proportion of the TRE team, Blumlein was testing the equipment on board a Halifax bomber on 7 June, 1942 when an engine caught fire. The plane crashed, killing all on board. Despite this catastophe H₂S was completed and produced for Pathfinder and Coastal Command aircraft.

Blumlein's reputation

Blumlein's name is not as well known as it should be. Most of his publications are in the form of patents, rarely easy reading, and his circuit inventions do not bear his name. But his work is all round us in stereo recordings, bridge measurements, television signals,

Plan-position radar, and the many circuits we use without realizing they are his, solely or jointly with others: the closely-coupled inductor ratio arm bridge, the cathode (and subsequently emitter) follower, the long-tailed pair, the transversal filter, the Miller/ Blumlein integrator and others.

M.G. Scroggie has summed up his character: "a grasp of essential principles, foresight, versatility, originality, soundness of engineering and insistence on 'designability'". Others have remarked on his honesty, integrity and humour, and his conviction of the importance of understanding fundamentals. "He would repeatedly - I remember it as clearly as if it were yesterday - be going back to Thevenin's theorem", J.D. McGee has recalled.

This fondness for Thevenin is remembered by several who worked with him. "One of his favourite devices was to bring a discussion to its close by quoting Thevenin's theorem, and he would often be half way down the corridor, puffing his pipe and shouting Thevenin' over his shoulder before we were able to gather our wits together," says Vanderlyn.

Once he forgot this ritual. The team duly presented him with a "Thevenin Medal" made from the lid of a cocoa tin. As far as I know it was the only medal ever presented to him by engineers.

His achievements would be a fitting memorial if better known. Despite one attempt, no full-length biography of him exists. The profession he served so well should put that right. Perhaps through the Institution of Electrical Engineers, whose meetings he graced, this omission could be corrected.