[GreenKeys] GreenKeys Digest, Vol 104, Issue 46

[John Nagle]

On 9/30/2012 1:47 PM, greenkeys-request at mailman.qth.net wrote:
> Message: 5
> Date: Sun, 30 Sep 2012 16:47:26 -0400
> From: "Lester Veenstra" <Lester at veenstras.com>
> Subject: Re: [GreenKeys] Just about all you need to know about
> 	Selector	Magnet Drivers
> To: <WA5CAB at cs.com>,	<greenkeys at mailman.qth.net>
> Message-ID: <035701cd9f4c$cde85a20$69b90e60$@com>
> Content-Type: text/plain; charset="iso-8859-1"
> 
> And now will someone explain the difference?

   What, pulling magnet and holding magnet selectors?

   To reduce the current required, some Teletype machines
had a "holding magnet" selector, where a cam pushed the
plate against the selector magnet poles once per bit
time.  If the magnet was on (MARK), the plate would stay
there, but if it it was off (SPACE), a spring would pull
it away.  It takes much less current to hold a plate
against an electromagnet than to pull it there from
a distance.

   I've seen a holding magnet selector for a Model 14 machine,
but haven't used one.

   Pulling magnets were wrapped in black, while holding
magnets were usually wrapped in green.



				John Nagle