The 60hz to 50hz solid state frequency converter is used for testing products to be exported and for operating imported plant equipment designed for 50hz. The 50hz to 60hz models are used overseas to test products destined for use in the US or other 60Hz countries and to operate 60hz machinery from a 50hz utility. The 50/60 hz to 400hz type is for use in aerospace applications. Visicomm Industries manufactures frequency converters and voltage output changers for sale and rental: Call toll free 1-866-221-3131 for more information on our power products and services.