This active tone control circuit was found in American documentation from the 90's. The transistor can be general purpose or low noise with high gain.
This circuit generates an ultrasound whose frequency is set in P1. Reproduction is done on a...
This circuit was suggested by General Electric / RCA in a 1980s documentation. The components are of...
The circuits shown in figure 2 are suggested by Texas Instruments (www.ti.com) make use of the...