The CHU660 Customer Interface Unit (CIU) is a cost-effective solution designed for users of split prepaid electricity meters, facilitating communication via M-Bus / RF. Equipped with a keypad and backlight, it enables users to input 20-digit tokens for top-up and to query various information such as energy consumption and remaining balance. This CIU also features balance and tamper alarm functions, contributing to the development of efficient smart home and AMI systems.