DoN. Nichols wrote:

My first exposure to op-amps was the plug-in modules with two
tubes which were used as part of the Beta testers on the transistor
production line. I had no idea how they worked at the time, so the
schematics rather puzzled me. :-) Trying to remember who made them, and
I *think* that it was Philbrick -- who also made ones with discrete
transistors in little metal bricks.


http://www.philbrickarchive.org/ has the history of their op-amp,
the GAP/R Model K2-W. I had one in my collection, but I don't know what
happened to it.

--
Subject: Spelling Lesson

The last four letters in American.........I Can
The last four letters in Republican.......I Can
The last four letters in Democrats.........Rats

End of lesson. Test to follow in November, 2016

Remember, November is to be set aside as rodent extermination month.