We found this configuration in a 1974 publication. Transistors can be replaced with equivalents such as 2N2222. The circuit has a dynamic range of 60 dB.
We found this circuit in a publication from the 1970s. It produces intermittent clicks on a...
We found this circuit in a Philips documentation from 1969. It makes use of transistors of the...
This circuit was found in a 1999 English magazine, but can be easily assembled with BC548...