We found this circuit in a 1967 IEEE documentation. The circuit uses discrete components of the time based on the 1.13 MHz frequency used with oscilloscopes at the time.
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...