Changes

One must differentiate between static tests (for ex. contact resistance) and dynamic ones (for ex. electrical life). In certain electromechanical components and switching devices the contacts can be exposed to both, static and dynamic stresses (for ex. connectors, relays, switches, pushbuttons, circuit breakers). For statically stressed components the life expectancy is usually expressed as a time period, i.e. hours, while for dynamically stressed ones the expected functional life is defined as numbers of operations or switching cycles.