Four-way answering device circuit schematic introduction:
A circuit consisting of two TTL integrated circuits and a few other components can indicate which of the four buttons is pressed first and prevents latecomers from entering. When one of the four Q outputs is logic "0", the corresponding LED illuminates while the clock input is at a low level to block other entrants. The schematic diagram of the four-way responder circuit is shown in the figure below.
Four-way answering device circuit diagram
Dongguan Guancheng Precision Plastic Manufacturing Co., Ltd. , https://www.dpowergo.com