Suggested by General Electric in an old documentation, this circuit can use modern SCRs and the transformer has a voltage according to the rail and current of at least 3 A.
This circuit allows the use of headphones and microphones with diverse characteristics in audio...
We found this circuit in the 1994 Linear Applications Handbook from National Semiconductor. The...
This circuit was found in Radio Electronics from the 90s. The transistor is for general use. The...