This circuit was found in a 1968 documentation. It makes use of both NO and NC reed-switches and small magnets attached to a card in the form that results in the drive combination.
In the figure we have the circuit of a multi-range ammeter using a 50 uA full-scale instrument. The...
We found this circuit in a Radio Electronics magazine from December 1969. The circuit uses a...
This blocking oscillator was found in a publication from the 50's. The coils determine the...