Michael Black wrote:
On Tue, 11 Feb 2014, Kafkaësque wrote:

Didn't semi-automatic keys use magnets for something? I remember seeing
an article about making one, and I remember magnets, even if I can't
remember their purpose.

I recall a good number of years back, 30/35, someone asking me to help with
such a key.

The magnets generated the relative di/dah length. I don't recall if it had
one or two paddles but it seemed to have a mass of adjustments to get it
right. There were other magnets to adjust the paddle(s).

It was beautifully machined but the electrical connections were terrible,
plus a few other things. I did the repairs and the OP twiddled the
adjustments, keyed away beaming ear to ear, and left happy offering all and
sundry as reward.