Luminous and sound probe circuit diagram

The NE556 timer circuit is connected to an oscillator by IC3 and controlled by IC1 (SN74132N) and IC2 (SN7486N). It can use sound to alert the static state of the digital logic measured point, which provides convenience for blind experimenters. When a logic transition occurs from 1 to 0 or from 0 to 1, as long as the duration exceeds 50ns, this circuit can detect it and report it with a "beep" sound. The light-emitting diode is for visual observation. When the input is logic 1, the light-emitting diode emits light.