8-way buzzer composed of CD4508

The specific circuit of the 8-channel buzzer made with CD4508 is shown in the figure below.　

How it works

When one of the buttons K1 to K8 (such as K3) is connected first, that is, the (8) pin of CD4508 is at a high level "1", the data is transmitted to the (9) pin, which is at a high level "1". After passing through the 8-input NOR gate/OR gate CD4078, its (13) pin outputs a low level "0" and sends it to the latch terminals (2) and (14) (ST1 and ST2) of CD4508. Therefore, the output data is latched, and the other buttons are invalid. At this time, the corresponding indicator light L3 is lit at the same time, and the answer is successful.

Press the reset button, the output data will be cleared, the indicator light will go out, and the next round of answering will begin.