True Story No32



In the mid-seventies the Company I worked for sent round a circular.

It explained that within the Industry there was a tacit understanding that one could design things without too much consideration of whether it embodied someone else's idea.

In order to get away with this our Company was supposed to pull its weight and invent things off its own bat.

Given an equitable balance of patents between the three largest competing Defence Companies of the day no-one would bother if they saw one of their ideas getting used by one of the other two.

The note went on to explain that we hadn't been bothering to patent our ideas lately and would we all think of something that we could register.

"A Patents Expert would be visiting us soon and would talk to those with ideas and explain what was required".

It so happened that I was leading a small team of engineers in the design of a data multiplexer for an Air Traffic Control system and the design used a few novel techniques.... eminently patentable!

I duly filled in a form.

Not so much for the glory of getting a patent awarded to me but because, for each patent awarded, the inventor would get paid the princely sum of £30.

This may not sound much when you consider the worth of the Zip Fastener and the like but in those days a good weekly wage was £50.

Because one invented something in order to do a job, for which one got paid, one couldn't go it alone and patent anything yourself, so any reward was better than nothing.

I called in the team and asked them what we should do.

At the outset of the Project I had carried out the basic design and the team was now developing it into a workable product.

The first patent was general.

As part of the design activity we had designed a general purpose microprocessor on a plug-in circuit board.

It used ordinary TTL integrated circuits, random access memory chips (RAM) and read only memory (ROM).

There were a total of ten of these used in a multiplexer in two types.

One type was used to read data input by Air Traffic Controllers, from things like tracker balls and sets of keys and switches.

The second type gathered the data together and sent it to a number of large computers.

The set of tasks for each was contained in ROM and could be modified during development until it worked properly.

The first patent was for a "Microprocessor Controlled Multiplexer".

The second novel idea was associated with the architecture of the multiplexer.

Communication between microprocessors was by a tri-state bus. This enabled any devices wanting to engage in the transfer of data to be easily coupled together. In effect by just joining their input/output wires with the system bus.

There were 256 such devices and when things were working all well and good but if one device failed or acted in a rogue manner it was very difficult to know which one it was. For example if one bit of the bus was permanently dragged down to ground potential.. how did one discover which device was responsible?

The answer was to insert a small resistor in series with each bus connection.

The resistors for good devices would have a different potential across them to the resistor of the rogue device.

By carefully analysing the noise immunity for the system we came up with a value for a suitable resistor and ordered these in dual-in-line form consistent with the design of the devices driving the bus.

The second patent was therefore for the design of a bus system which could be quickly tested and put right if it failed.

I note that this has recently been "invented" again by a large processor manufacturer, 25 years after our patent was accepted.

The third patent was a method of asynchronous signalling between remote computers.

This used normal start-stop serial code with a variable number of stop elements.

Usually a single stop element is used. Sometimes "one and a half" elements are used and sometimes two. Our design used both one and two stop elements. The latter for marking specific bytes in a sequence.

For example if you wished to transmit 24 bit data blocks using a standard design of chip (a UART), the 24 bit word would be divided into three equal parts (or bytes). The first two parts were given a single stop bit and the third two stop bits. When the UART detected two stop bits it signalled the receiving device which was able to re-constitute the 24 bit data blocks.

The design was able to detect errors and worked as reliably as a normal 8 bit data transmission system.

The chief advantage over other potential techniques was speed.

Our system worked in real time and needed to provide 100% reliable information to the Air traffic Controllers without delay.

We also had a fourth patent-able idea.

At that time there was no easy way of inserting very large chips into sockets, or for that matter, extracting them later.

We had developed a simple device for these purposes. It was so useful the patent expert decided not to disclose it as our competitors would have copied the idea and gained a worthwhile advantage.

How to proceed?

Well although we got £30 for each patent we had to spend a not inconsiderable time preparing a paper describing it, and having done this, liaise with the Patent Expert until it was finalised.

The answer lay in the wording of the note that had been circulated.

Each patent could be requested jointly by two people and both would get a full £30.

So in a stroke team morale was given a boost.

For each patent I nominated a second engineer.

For £30 he could write up the proposal.

So from our four ideas I got £120 and four other engineers got £30 each.

If you know how to interrogate the UK Patents Database you could look up the three that where awarded patents.

I'd have imagined that someone has probably re-invented a "microprocessor controlled multiplexer" by now; somebody certainly has re-invented the bus fault detection method and maybe someone has even worked out a new communications technique using variable numbers of stop bits.

The Company I used to work for no longer exists and I got my £30s so who cares?

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