This flip-flop circuit with general purpose transistors was found in American documentation from the 1980s. The maximum operating speed depends on the transistors. Diodes are commonly 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...