This circuit has an automatic dynamic gain control in a range of 6 dB to 40 dB. We found it in documentation from the 90s. The bipolar transistor is a general purpose type.
This circuit was obtained from an American 80's documentation. The transistors can be 2N2222 and...
This circuit was found in Motorola documentation from the 1980s. PUTs are not common components...
This circuit is based on an uncommon Texas component today, as found in an American 1980s...