Magnetic amplifiers are commonly referred to as 'Mag Amps'. Invented in the 20th century, magnetic amplifiers were used as device to amplify electric signals. The magnetic amplifiers were used as an alternative to vacuum tubes amplifiers where robustness and high current capacity were required. The advantage of magnetic amplifiers is that they are highly reliable hence they work efficiently in applications that require high reliable amplifiers. Another important high point of a magnetic amplifier is that high isolation voltages can be achieved between windings and proper design. Even today magnetic amplifiers are still preferred over semiconductor devices in certain safety critical applications.