R1 may be 10k and R2 100k. The transistor can be the BC548 and instead of the small lamp we can use a series LED with a 1k resistor. D1 is germanium and C1 is 10 nF. C2 can be 47 nF.
This circuit was found in American documentation from the 90's. The circuit applies to any...
We found this circuit in an English publication from 1980, but it can be assembled with BC548...
This circuit was found in the 1991 Electronics Experimenter's Handbook. It activates a relay when...