As edde says but to expand a little...
The UCH (Unite Centrale Habitacle) is an electronic control module that is fitted to many late model Renaults (early 2000's onwards.) It is responsible for controlling many of the non-engine related functions of the car, such as central locking, electric windows, and even some of the lights (e.g. indicators.)
A brand new UCH is supplied with a blank memory. This must be coded (using the Renault Clip computer) to match the serial number of the ECU and key/card before it will work with the car. The memory can only be written once, so a used UCH cannot be taken from a donor vehicle to be used in another unless the ECU and keyfobs/cards are also transferred.