We found this circuit at Popular Electronics. The components are still current. Changes can be made to obtain higher voltages, as indicated in the second diagram.
This network can be used in a sound project to control the tone. The circuit is from an...
Published by Philips in 1965 documentation, the sensor for this circuit is a common LDR. The...
This circuit operates at a voltage of 1.3 V from a single mercury cell. We found in an old...