The testing consists of two parts:

1. Interoperability relates to the ability of Type 1 devices to interact with the Data Communications Company (DCC), successfully receiving, interpreting, acting on and responding to messages.
2. Interchangeability goes further, checking that all devices on the Home Area Network (HAN), such as meters and pre-payment interface devices, can communicate with one another, interpret and act on commands, no matter what brand is being used.