A component of machinery that is charged with either controlling a mechanism or moving it in some way, an actuator may be used for regulating pneumatic or hydraulic pressure as well as operating entirely electronically. Whichever type, an actuator needs two things: a control signal and an energy source. Manufactured by companies such as SMC, Kuhnke and TDS, there are various types of electronic actuators on the market, each designed for specific purposes. Some act as shock absorbers, for example, while others are solenoids, designed to operate a mechanism when a signal power is received, such as electronic locks. Comb drives, servo-mechanisms, piezoelectric actuators and even simple electric motors are all types of actuator, as well. When selecting an actuator for a particular job, two primary attributes should be considered: static and dynamic loads. The static load is best described as the force capability of the device when it is not operating, while the dynamic load of any actuator equates to its force capability when it is working. Finally, actuators offer various degrees of movement which are referred to as their lifting maximums.