The dimensions and tolerances for connectors, appliance inlets, appliance outlets and plug connectors are given in standard sheets, which are dimensioned drawings showing the features required for safety and interchangeability. Mains appliance couplers The mains appliance couplers are all engineered to connect an appliance via a power cord to mains power. C1/C2 coupler The C1 coupler. OverviewIEC 60320, entitled "Appliance couplers for household and similar general purposes", is a set of standards published by the (IEC) that defines non-locking appliance couplers fo. Appliance couplers enable the use of standard inlets and country-specific cord sets which allow manufacturers to produce the same appliance for many markets, where only the cord set has to be changed for a partic.