Ivor Catt,

Electronics World,

August 2004, p57

and November 2004


The Catt Question


Analysis   State of Play   Political Analysis

Carver Mead   Mead   May04



Letter to the Editor, Electronics World,

published August 2004, p57;


The Catt Question - The EW Challenge.


Two letters in the July issue prompt me to take a major initiative, and to relegate my replies to the www in the hope that our editor will be able to publish them later. For the present, they are at the bottom of


Regarding "The Catt Question", EW reader Alan Robinson favours the "Westerner" answer of Dr Neil McEwan, Reader in Electromagnetism, while the second letter writer Ian Darney favours the "Southerner" answer of Pepper FRS. They reinforce our concern that the question is unresolved.


For many years, for instance in the pages of Electronics World, I have offered a large sum of money to any student who succeeds in getting his accredited lecturer or text book writer to write a signed, dated document discussing "The Catt Question", to no avail. Now the offer is put on a firmer footing.


I have opened a bank account containing £2,000 which our Editor can access. This is the prize behind the EW challenge.


I suggest to the editor that “Accredited” should mean Reader in Electromagnetism, author of published text book from mainstream publisher, or similar. Professor of Electronic Engineering will do, but not Professor of Electrical Engineering.


My advice to the Editor is that the first student who succeeds in getting his accredited lecturer or text book writer to write, sign and date meaningful, intelligible comment on "The Catt Question" should receive the first prize of £500. The next ten successful students should receive £100 each.


A student who provides documentary proof that his accredited lecturer or text book writer refused to make meaningful comment should receive £50.


Prizes should be paid out until the money runs out. Any third party contributions will be added to the fund.


In due course of time, all written, signed, dated comment (and all proof of refusal to comment) will be reached via my website at .


Only written comment the whole of which our editor understands can receive a prize.


The challenge is open to the whole world. All comment must be in English.

The decision of the Editor is final.


Ivor Catt



3aug05. No student in the world has had enough courage to send anything in writing to the Editor of "Electronics World". Ivor Catt.

18June 2007.For three years, no student in the world has had enough courage to send anything in writing to the Editor of "Electronics World". Can you guess why? Ivor Catt  

Letter to the Editor of Electronics World originally for publication in the August 2004 issue, replying to letters in the July issue. [This reply by Catt was not published.]


Q. How did Electra Robinson travel to London?

A. I know you are asserting she came by train.


In his letter in EW July04, p52, Alan Robinson writes;

"Catt flap 1

.... The crux of his renamed 'Catt question' is this assertion ...."

It is not. A question is a question. Pepper FRS and Dr Neil McEwan, Reader in Electromagnetism, give contradictory answers. See and  2813 . “It is an anomaly between rival textbooks and professors [Pepper and McEwan].” - Editorial, Electronics World, August 2003, p3. In April 2004 I wrote; "It took many years of painstaking work to elicit a single reply from each of two luminaries, who totally contradicted each other, and then went silent. All other accredited 'experts' also remain silent." In February I wrote; "Catt is not involved, except as an anxious student of these luminaries." In his letter, Alan Robinson supports McEwan.


On the same page as Robinson, Ian Darney cites a document which supports Pepper FRS. I have assembled lists of luminaries into the two groups, Southerners after Pepper and Westerners after McEwan.


Since writing my Exclusive OR article in the July issue, I have remembered that I had made a previous attempt to get the Exclusive OR (XOR) into a logic family. In Motorola we were committed to ECL. I was brought into Motorola in 1964 to address possible new problems with our ECL logic gates, which had a propagation delay of 1.35nsec. Previous logic, for instance the then current TTL, had a propagation delay of 10nsec. Motorola crossed the threshold when the delay through a gate fell to less than the delay across the system, 6in/nsec in an epoxy glass board.

Coming direct from Data Product Corp., I entered a community that was expert in semiconductor electronics, but admitted ignorance of digital system design, which is why they hired me. They created families in the tradition of the books on logic design, and also copied other companies’ approach. I noticed that the bistable they had built for their ECL range could be converted into an XOR gate with only one small change in the top layer of metallisation. They refused to do this, because the gate was not in Boole.

The D type bistable worked by using a lower long tailed pair to switch the current out of the bistable proper into one or other of its collector resistors, and then returning the current. The bistable itself was a cross coupled long tailed pair. The two long tailed pairs had common collector resistors. Two long tailed pairs with common collector resistors were also the essence of an XOR, dumping the current into one or other collector resistor.


This bistable had a propagation delay of 3nsec. I called it the “Murray bistable” because Don Murray, my co-author, invented it. However, this naming was prevented because Walt Seelbach, deputy head of R&D, thought he needed to be given some of the credit. It never got a name, although I thought its design was brilliant and should be patented under Don Murray’s name.

Ivor Catt

St. Albans




Reply by Catt to a letter published in August 2004.


Andy Holt discussed the XOR, saying it is not fundamental because it can be built-up from AND/OR/NOT. This argument could also be used against regarding OR as a fundamental operation because it can be built-up from AND/NOT. A discussion of the role and importance of the XOR is given in my 1968 article . Both AND and OR could be argued as doubtful as fundamental functions because, as De Morgan says, they mirror each other. However, for me, the fundamental set is NOT/AND/OR/XOR, as I show from first principles. As I say in my July article, I used the XOR a great deal when it was available.

Ivor Catt




Letter to those responsible for electromagnetic theory.

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