Galileo is Europe’s programme for a global navigation satellite system providing a highly accurate, guaranteed global positioning service. DSI has developed several EGSEs and SCOEs for the Galileo Common Security Box. It includes a large number of different interfaces and is used to test all on-board functions and redundant components simultaneously. The EGSEs and SCOEs are specially designed to operate in a restricted area and are TEMPEST-approved. The design allows the splitting of the hardware interfaces from the processing part of the EGSE by means of fibre-optic links. Through this, greater distances (e.g. 50m) can be reached.