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.
We found this circuit at Popular Electronics. The components are still current. Changes can be...
This circuit was obtained in a 1965 American magazine translation. The coil is formed by 40 + 40...
Found in 1968 Mullard documentation, this circuit uses period components. The transistors are...