This circuit converts a high voltage into a frequency using an optical coupler. The transistor can be 2N2646 and the coupler admits equivalent. The circuit is from a 1974 publication.
This configuration was found in an old technical documentation from the 70s, but it can be...
In the figure we have a converter that generates a negative voltage from a positive voltage...
This circuit was found in a 1976 magazine. The circuit emits a sound when a balance sensor placed on...