warning lamp with Euro lights

[Phil Payne]

> reed switch...glass tube c. 1" long 1/8" dia...has two
> contacts inside that can be made to close with a
> magnetic field, they are often used in burglar alarms,
> (magnet fixed to door, switch fixed to frame)
>
> they will also operate with a few turns of wire
> carrying 5A dc. ie the sort of current indicators take

The contacts are softish iron., usually silver plated.  In a magnetic field, they attract each other and make the circuit.  The IBM
026 and 029 Card Punch machines from the late 1960s contain DOZENS of the things.

--
  Phil Payne
  http://www.isham-research.com
  +44 7785 302 803
  +49 173 6242039