Design and Construction (4) Additional Equipment: Firefighters may also have a range of additional equipment available to them, which may include: Two-way radioThis is one of the most important pieces of equipment. Many services have moved from traditional UHF/VHF sets, which can be monitored externally, to more secure systems, such as those working on a GSM system, such as TETRA. (a) Mobile data terminalMany appliances are fitted with Mobile Data Terminals (or MDTs), which are connected wirelessly to a central computer, and enable firefighters to call up details such as incident logs, maps of locations, or exclusion zones. (b) Evidence-gathering CCTVSome fire vehicles can be fitted with video cameras used to record activity. They may also be fitted with sound recording facilities. This is used for the protection of the crew (and evidence of any assaults or intimidation of the firefighters) or can be used as evidence relating to the incident itself. (c) Ramming padsThese rubberized pads are fitted to the chassis of the appliance, to allow the vehicle to be used as a battering ram, or to push other vehicles off the road in an emergency. One of the uses of ramming pads is to remove a parked car illegally blocking a fire hydrant that is needed by fire crews responding to an emergency