Building a Lockout Buzzer System without Arduino

Thread Starter


Joined Dec 7, 2013
Hello Everyone!

I am a novice with circuits and want to get better with analog in particular. I want to build a lockout buzzer system wherein after the host pushes a button the contestants are allowed to push their buzzers, then the first buzzer to be pushed has an LED light up for that contestant, but all other buzzers that were pushed after this did not register (their LEDs do NOT light up).

This is a pretty simple concept and after looking up schematics online i am pretty sure it wouldnt be too hard for a novice like me to build. But so many of the things I have read use an arduino. Is there a way to build this system without a microprocessor?

My first instinct was to use PFETs that connect to every buzzer except the designated player. So when player 1 pushes their buzzer, it activates the PFETs from the each other contestant making open circuits and thus not lighting up their LED. The only problem is then this doesnt stop someone from pushing their button and activating the PFET on the first players buzzer....

Is there a simple way to build this with analog parts? Or is the microprocessor basically the only way?


Joined Nov 23, 2012
You could have all contestant buzzers connected to a flip-flop. Before each round, the host pushes his button that resets all three flip flops at the same time. Each contestant button is connected to their own flipflop set pin. The output of each flipflop is connected to an LED AND the reset pin of their opponents. The first to push their button sets their own flipflop and that output stays on in a flip flop. By staying on, it holds the opponents flipflop in a reset stat so they cannot be set. I am 90 % sure it will work this way.


Joined Apr 11, 2010
I have a completed game show circuit in the "Completed Projects" section. Look at this post.

From the post's introduction, "My sister and wife are in education, and the kids play a "Jeopardy" like game in the classroom. I wanted to make a circuit for them to use. After seeing several threads regarding game show circuits and attempting (unsuccessfully) to simulate many of them. I decided to attempt my own.

My circuit is for four players, and once anyone had pressed his/her button, their LED will illuminate and the circuit will lockout from any other inputs.

I used a 4013 D-type flip flop with the clock connected to a push-button input (more on this in the next paragraph) They clock on the rising edge. The D input is tied high, so that starting from a reset state (Q is low; Q' is high), the Q output will go high on a rising edge. The Reset inputs are held low with a pull-down resistor, and will reset when the input is brought high.

Locking out other players when one button is pressed is done by first sending the clock input through an dual input AND gate. The second input of this gate for each player is tied to the output of a quad input AND gate, whose inputs are driven through Q' from each flip flop. Thus, when one player buzzes in, his Q' will go low, all the AND gates will prevent input to any clock, thus effectively locking everyone from changing the state.

The post contains a parts list with numbers, a schematic, an ExpressPCB file for the PCB (or I may have one left over; talk to me)