Manual pulse generators (handwheels) institute a command pulse when a handle is turned manually. They are sometimes used to position the axes of milling machines and other industrial equipment such as turns and lathes. A portable manual pulse generator or handwheel can be used to calibrate multiple machines or devices. A manual clock pulse generator circuit is often used to generate standard clock pulses. Continuous wave generators and signal and sweep generators are common alternatives to manual pulse generators and handwheels. Quasi-continuous generators can be used in both pulsed electron spin resonance (ESR) and electron paramagnetic resonance (EPR) applications. Performance specifications for all types of pulse generators include frequency range, pulse duration, and typical output power. Durability is an additional factor to consider when selecting manual pulse generators or handwheels.