This circuit filters low frequency noise from the turntable motor. We found it in a 1989 documentation. The font doesn't have to be symmetrical, but it should have excellent filtering.
The figure shows how to implement an alarm buzzer in an LM3914 to warn about crossing the scale...
This circuit can act as a shield being controlled by a microcontroller by pin 1 or 2. The...
This circuit was obtained from a 1980's QST magazine. The circuit can generate 1 to 15 MHz signals...