This cassette player motor speed control was found in the January 1991 issue of Radio Electronics magazine. The circuit is for voltages from 9 to 12 V.
This filter that rejects determines frequency (notch) was found in a Popular Electronics of 1993....
This circuit operates with frequencies from 0.5 to 400 MHz. We find it in a 90’s NASA...
This circuit for adjusting sources simulating a load was found in a publication from 1993. The...