Abstract: A linear actuator (20, 20?, 20?) comprises a plunger receptacle (22); a coil (24); a magnetic plunger (26); a magnetic base (28); a return spring (30); and a lock spring (32, 32?). The coil (24) is wound about at least a portion of an exterior surface of the plunger receptacle (22). The magnetic plunger (26) is at least partially disposed within a cavity at least partially formed by an interior surface of the plunger receptacle (22) for linear motion along a plunger axis (34). The magnetic base (28) is radially disposed relative to the plunger (26). The return spring (30) is disposed to bias the plunger (26) to a plunger extended position. The lock spring (32, 32?) is configured and oriented to lock the plunger (26) in the plunger extended position when power is not applied to the coil (24) but to be attracted to the magnetic base (28) and thereby permit movement of the plunger (26) to a plunger retracted position when the power is applied to the coil (24).