Use an fault tree analysis $($FTA$)$ to redesign a simple system to meet a customer's criteria.

Review the diagram of the simple electrical doorbell. This system is comprised of three basic components: the bell and clapper, the button, and the power supply. Each component has a failure rate of $1$ in $1000$ operations, or $1103.$

Because you only need one of these components $($OR gate$)$ to fail for the system to fail, the probability of this system's failure is $3103$

Redesign this system so the failure rate is less than $5$x$10^-6,$ or less than $5$ in a million operations.

Please assist me in creating a Fault Tree to demonstrate the new system's reliability.

You will not need any new parts or components but will likely have some redundancy of the existing parts in your new system. Photo Credit: Michael O'Toole, Professor Emeritus, ERAU Example Doorbell Failure FTA

Photo Credit: Michael O'Toole, Professor Emeritus, ERAU