[GreenKeys] Starting Up an Old Debate

[jhhaynes at earthlink.net]

There's nothing wrong with the saturation idea; we just don't know if
Teletype used it.  When the core goes into saturation the incremental
inductance collapses; but the strength of the magnet is no less than
it was at the onset of saturation.  

According to Walt Zenner, who got the patent on it, the original reason
for the holding magnet selector was th reduce the voltage on the cord
circuits in the TWX switchboards.  With the earlier machines they were
using 120V on the switchboard cords, where it is exposed to the operators'
hands and can be deadly.  So the holding magnet selector allowed them
to run 48V on the cords.  That still seems pretty high, but was no
higher than the voltage on telephone switchboard cords.

I've just received a notebook on magnet design that belonged to some
early Teletype engineer.  I'll scan it and add it to the Teletype
Scrapbook CD ROM, and maybe will send out some individual page scans
on the list.



-- 

jhhaynes at earthlink dot net