This circuit is from an old American documentation using as indicators for the flip-flops neon lamps. This way, the circuit has two supply voltages.
This circuit keeps the neon lamp on for a moment when it receives a pulse. The turn on time...
This circuit was found in General Electric's 1965 documentation. It appears elsewhere on the site....
This configuration was found in a 1990s documentation. Modern operational amplifiers can be used...