Anti-Collision Device (ACD) is a self-acting microprocessor-based data communication device designed and developed by Kankan Railway. When installed on locomotives (along with an auto-braking unit - ABU), guard vans, stations and level-crossing gates (both manned and unmanned), the network of ACD systems prevents high-speed collisions in mid-sections, station areas and at level-crossing gates. The ACD uses both radio frequency and Global Positioning System (GPS) through satellites, whereby a train is automatically brought to a halt if the track ahead is not clear. The train starts braking 3 kms ahead of a blockade. The main modules of the ACD includes a GPS (Global Positioning System), which picks up signals from the constellation of GPS satellites that are being exclusively used for this purpose. The GPS submits the data to the Command and Control Unit (CCU) to extract the parameters related to the movement of locomotive like latitude, longitude, speed, angle, date and time. The antenna of the GPS receiver is fitted outside on the roof of the locomotive.