IIH Generator: a 2001 perspective

These musings are written on 23/6/2001 T:=01:24 PST, roughly on the 26'th anniversary of this devices construction. It was my first large scale digital circuit and, considering that my major in 1975 was honors physiology, I am rather proud of the fact that I did manage to get this device finished and that the arrogance I exhibited in doing an electronic engineering project in place of a physiology project was rewarded with praise rather than the censure I could have reasonably expected. This device also performed a potentially usefull function in 1975; it is now obsolete, but the eclectic areas I chose to explore in 1975 have served me well in my subsequent scientific career.

IIH generator is also the only circuit from that era that I fully documented; I didn't have much choice since I had to hand in my 4th year project before I started my summer job as part of a biophysical survey of Nahani National park from July-August 1975. As I had been totally immersed in getting the circuit together for several months, I rounded up a few friends, and with large quantities of beer and other pharmaceuticals we proceeded to use an optic fingertip heartrate monitoring device to acquire large numbers of cardiac activity histograms under various physiologic and psychologic states. These have not been analyzed and likely never will be as it would be simpler to repeat the experiments using a computerized system instead of my IIH generation device which required output of the cardiac histogram manually in octal form bin by bin; I'm not sure how valid my records are as we did drink a lot that day.

In my future electronic endeavors, there never seemed to be enough time for documentation as once I finished designing and building a circuit, it was time to move on to something else. Thus, the documentation for IIH generator is more complete than any subsequent digital logic project I have done since 1975. The other unique thing about 1975 was that this was well before the era of easily available microcomputers. My income at this time was about $240/month, and the cost of an 8080 was about $250. My experiences with MOS IC's at this point had not been very positive as they were nowhere as forgiving as the DTL/TTL I was used to playing with. I was probably correct in making the choices I did for, while a microprocessor could have performed everything I needed to do using software rather than hardware, I could not afford to blow a single CPU chip. Also, programming of a microprocessor system would have been done entirely using toggle switches and the time required to make a working system would not have been any less than the design of custom digital logic to perform the desired function.

This HTML version of the 1975 report is also an experiment in how to deal with pre-digital format information in the digital age. Written records on paper seems to be the only storage medium that doesn't become obsolete when one considers the technology required to access stored information. My programs stored on paper tape are inaccessible unless I build a paper tape reader, and I really can't be bothered. Similar access difficulties are exhibited by my programs which exist on punched cards. What is most annoying is that the "modern" data storage medium I embraced from 1978-1987, 9 track digital tape, is now impossible to read. My digital copy of my MSc thesis is on a magnetic tape which may be unreadable before I find a 9 track tape drive to transfer the data to a medium my computer can read. I did read my thesis onto a PDP-11 hard disk, and translated it from EBCDIC to ASCII, but I needed to clear off space on the disk and so I wrote back the ASCII data to another 9 track tape. I have a paper copy of my thesis and I've scanned it into my newest computer, but no OCR program I have found is capable of decoding the lineprinter fonts from 1978. This is a digression.

What I have decided to do recently is to make all of the circuits and programs I have built available online. It may be that someone will find these items usefull, but I think it is more important to document that remote past which becomes more recent with every passing year. I have no illusions that someone will make use of the work I did in 1975; it might, however, have the effect of invalidating certain trivial patents as it does represent prior art. It also represents a means of archiving this material for myself as there will likely come a time when I can no longer physically store these materials, and the digital record of what was will be all that there is.