This circuit was found in a 80’s American documentation. The adjustment trimpot is from 47k to 100k. The diodes are general-purpose types use and the supply voltage depends on the relay.
The circuit shown is from the Motorola Linear Databook from 1990. The circuit has two outputs with...
This rejector filter that was found in a 1980 documentation uses an operational one at the time....
This fuse test circuit was found in Radio Electronics magazine from August 1958. The circuit was...