25 Sep
2004
25 Sep
'04
6:09 a.m.
Tony Duell wrote:
There were/are also relays with 2 coils. The idea is that either coil
alone will activate the contacts, but if you energise them both together
(in opposite directions), the magnetic fields cancel out, and the
contacts don't operate.
And of course there are magnetically-latched relays (effectively SR
flip-flops).
-tony
And slugged relays, with a big metal ring in the coil. These either
delay opening or closing, but I can't remember which way round it works.
I've got a few from old telephone exchanges - when I was about 12 or
13 I convinced my Dad to take a pickup truck full of BT phone exchange
"modules" from the local scrapyard.
Gordon.