If you had that circuit in a box that you couldn't look into, and instead were limited to giving someone a list of specific signals and having someone tell you the voltages of those signals, what signals would you put on the list, keeping in mind that there is value in keeping that list as short as possible.

 

In other words, what is the least number of signals in your circuit that show the output has reached 00?

 

U1-11 and U14 are in conflict. You cannot do that.

 

U1-11 and U14 are in conflict. You cannot do that.

actually I did it, I used 2 8 input NOR gate, one is connected to the base of transistor, one si connected to the clock (DN) so when the timer reach 00 from the timer it will send low signal, but with the used of NOR gate. The low signal became high and that triggers the transistor to buzz

 

Have you looked at what TCD on the counted IC does?

 

Have you looked at what TCD on the counted IC does?

I think it is used for cascading TCD if the count is down TCU if up then connect the TCD/TCU to the DN/UP

 

I think it is used for cascading TCD if the count is down TCU if up then connect the TCD/TCU to the DN/UP

Read the 74192 data sheet and determine at what count TCD changes state.