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 simple circuit with a 5V regulator was found in an American documentation from the 90's. The...
We found this circuit in a Radio Electronics from February 1966. The transistor is from the time...
Assembled with SMD components this circuit can be very small. The range is a few tens of meters. We...