This power supply for those who want to feed and recover 5 ¼ floppy disks was found in the Electronics Experimenter magazine special edition of 1983.
General Electric suggests this circuit in a 1980s documentation. The operational of the time is...
This circuit, from a 1973 publication, locks the relay when the light that falls on the LDR is cut...
This circuit can be adapted to an FM radio or other receiver that does not have a tuning indicator LED....