Automatic Transfer Switches are required for standby, back-up & emergency power installations. A Transfer switch is installed between a backup generator, incoming power and your business. A transfer switch continuously monitors utility power and when it senses an interruption it sends a signal to start the generator, when the generator is up to the proper speed, Hz and voltage the transfer switch transfers the load to the generator to provide emergency power. When utility power is restored and no interruptions have occurred for a set time, the transfer switch will then transfer back to utility power and send a signal to turn off the generator after a specified amount of cool down time with no load on the generator. A properly installed automatic transfer switch allows safely switching from utility power to emergency generator power while maintaining isolation of each source from the other. A transfer switch is required National Electric Code in all 50 states for back-up / emergency / stand-by generators and is an essential piece of safety equipment.