This circuit was found in a 90s American publication. The same configuration appears in several places on this site, obtained from different sources. The lamps can be replaced by LEDs.
This circuit, obtained from a 1965 magazine, can still be assembled using some modern equivalent...
The LEDs act as diodes, so if good they will show the same characteristic curve. Arrangment shown...
We found this circuit in an ancient American documentation. It can be adapted to operate in other...