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.
I found this circuit in an English magazine from July 1982. The circuit is still viable by using...
The circuit shown was found in the 1994 National Semiconductor's Linear Application Handbook. The...
This solar powered circuit was found in a 1991 documentation. The transistor is a general purpose...