A time invariant system is one that given a shifted input, the only effect is a shifted output. x(t) -> y(t) x(t-T) -> y(t-T) An example of a time variant system y(t) = 2(x(t)) x(t) = t if T = 1 and if t = 5 then x(t)or 5 ->[2x(t-T])-> y(t) or 8 x(t) or 5 -> y(x(t))-> [y(t-T)]->2x(t-T)-> y(t) or 8 An example of a time variant system y(t) = t(x(t)) x(t) = t if T = 1 and if t = 5 then x(t)or 5 ->[tx(t-T])-> y(t) or 20 x(t) or 5 -> y(x(t))-> [y(t-T)]->(t-T)x(t-T))-> y(t) or 16