In reliability mathematics, the reliability rate of equipment is represented by k and the failure rate by g, so K+G= 1. Series system reduces the reliability of the system. The two same reliability rates are K 1 and K2. After series connection, the reliability k is K 1K2, and the failure rate g is 1-K 1K2.

If the reliability of the original system is 99.9%, after two identical systems are connected in series, the reliability becomes 99.9%x99.9%=99.8%.

The parallel operation of two systems with the same function is called redundant system, which can improve the reliability of the system. The two same reliability rates are K 1 and K2, and their failure rates are G 1= 1-K 1 and G2= 1-K2, respectively. The reliability of parallel connection is K = 65438+.

If the reliability of the two systems is 90% and the failure rate is 10%, then after the two systems are connected in parallel, the reliability rate becomes k =1-10% x10% = 99%.