[GreenKeys] Wrong cam on model 15

[Harold Hallikainen]

On Sun, September 15, 2024 2:06 pm, Jim Haynes wrote:
> You can read a lot of hand-waving stuff about the holding magnet selector
> being more sensitive, which I guess it is.  But the reason for it,
> according to the inventor, was in connection with TWX cord switchboards.
> This was from Walt Zenner, who was VP for R&D at Teletype for many years.
>
> The pulling magnet selector canonically required a 120 Volt loop.  In
> TWX switchbords this voltage appeared at the exposed switchboard cord
> tip and was dangerous to the switchboard operators.  The holding magnet
> selector could be used satisfactorily in a 48 Volt loop.  That voltage
> was already being used on voice switchboard cords, so at least it made
> the probability of getting killed at the TWX switchboard no greater than
> what it was at a voice switchboard.

Interesting! Since holding magnets let you put the coils in parallel,
resulting in 1/4 the inductance of when they are in series, I think that
would work! Since T=L/R, the lower inductance would let the series
resistance be 1/4 as much to yield the same time constant. That would
allow you to get 60 mA with 1/4 of the original 120V, or 30 volts.

While in high school, I had several model 15 and Kleinschmidt machines. I
ran a wire through trees to a friend's house. We set up a teletype loop
with that wire and ground. I first tried running it with a 12 volt loop
supply. I could get the 60 mA, but garbage was printed. That's when I
learned T=L/R!

Again, interesting!

Harold
https://w6iwi.org


-- 
https://w6iwi.org