[GreenKeys] Historical instrument catalogs

[Douglas W. Jones]

On Aug 22, 2004, at 8:56 AM, Craig Sawyers wrote:

> Hi all
>
> While poking around on the web, I found a superb collection of
> manufacturer's catalogs from the late 1800s to the early 1900s.  
> Included
> items in the Cambridge Scientific Instruments catalog of 1908 is a 
> "Hertzian
> wave detector" - basically a diode.

I've been slowly searching out the International Correspondence Schools
handbook series from that era, I have their building trades handbook,
their electrical engineering handbook, and their handbook or telephony
and telegraphy.  The latter, pre World War I vintage, has a wonderful
writeup on radio in the final chapter, full of great descriptions of
such speculative wonders as the Audion as well as schematic diagrams of
the state-of-the-art Marconi morse code sets of the era.  This also is 
the
stuff that was on the Titanic.

One fascinating thing to see is the state of evolution of the schematic
notation we now take for granted.  Back then, in the belle epoch, they
clearly had rudiments of our now-standard schematic notation, but it was
still presented as halfway pictorial.  The open circles representing
contact points to the outside world still had a screw-slot drawn across
them, for example.

Another interesting thing to note is the state of understanding of tuned
circuits.  They clearly understood that capacitors passed AC while 
blocking
DC, and they clearly understood that inductors passed DC while blocking
AC, but when both were present in the same circuit, the explanations 
always
seemed to get a bit muddled.

One paragraph in the section on radio talks about the debate about 
whether
tuned circuits are better than broadband.  This was a debate, and there
were strong proponents of untuned morse who, it appears, really didn't
understand tuned circuits well enough to see any benefit to them.

		Doug Jones
		jones at cs.uiowa.edu