Found in an old publication about neon lamps this circuit works directly connected to the power grid, serving as an indicator for various situations. Ordinary neon lamps can be used.
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...