The basic principles: Instrumentation in the YX series of electric contact pressure gauge on the installation of small relays, so that the original contact by touching a point move, two relay linkages. Line is simple, safe and reliable. Because of the small relay coil power rarely, table of basic non-contact sparks, relay contact current to 3-5A, may be called the power on. After years of experience, such as proper use of funds, use of 5-10 years. The device for the lower limit of normally closed (starting), the upper limit for the regular open (stop), coil for 220VAC. Can also be customized into other voltage, other patterns, such as double-ceiling, double the lower limit, lower limit of regular closed, normally closed two-limit, normally closed, such as double the minimum.