A:Answer Electro-mechanical controls were used in the past before computerized devices. An Electro-mechanical control is a rotary multi selector switch operated by a small timer motor, it can also be advanced manually by turning the selector knob. Normally the selector knob can only be turned clockwise. The switch was reliable and not subject to all the electro statics that blow up computing devices. The quantity of failure points for the mechanical switch is about 10,000 less failure points, but each device has about a 100 year life versus the switch components that each may have a 15 year life. Expect a switch to last 25 years and the computer control device to last about 5 years..
