1、 measure active electric energy, needn't to be corrected after working a long time. 2、 Purchase electricity first. 3、 Record information of power utilization. 4、 One card for one user, anti electricity-theft. 5、 Alarm for lack of residual electricity. 6、 Display residual electricity, accumulate and alarm electricity 7、 Can read user power utilization information backward 8、 Test pulse of electric energy output. 9、 Specified working temperature: -10~45degree. Utmost working temperature:-25~60degree. Relative humidity must less than 85% at environmental temperature 23degree and there shall be no harmful substances causing corrosion in the air.