This interesting circuit was found in an 80's Electronic Engineering. The circuit has a 50% active cycle. R and C determine the generated frequency.
This circuit is from a publication of the 70s, but it can be easily assembled with the BC548. The...
This very low frequency amplifier has a gain of 1,000 and was found in a 1967 documentation. The circuit is...
This transmitter was found in a 1993 documentation, but it can be assembled with operators like...