emergency vehicle in their rear view mirrors. The vehicle may also display the name of their owner or operator, and a telephone number which may be used to summon the vehicle. Ambulances may also carry an emblem (either as part of the passive warning markings or not). Some ambulances may display a Red Cross, Red Crescent or Red Diamond (collective known as the Protective Symbols). These are symbols laid down by the Geneva Conventions, and all countries signatory to it agree to restrict their use to either (1) Military Ambulances or (2) the national Red Cross or Red Crescent society. Use by any other person, organisation or agency is in breach of international law. The protective symbols are designed to indicate to all people (especially combatants in the case of war) that the vehicle is neutral and is not to be fired upon (see Military ambulances), hence giving protection to the medics and their casualties, although this has not always been adhered to. Many ambulances use the Star of Life, which indicates that the vehicle's operators can render their given level of care represented on the six pointed star. Active visual warnings The active visual warnings are usually in the form of flashing coloured lights (also known as 'beacons' or 'lightbars'). These flash in order to attract the attention of other road users as the emergency vehicle approaches, or to provide warning to motorists approaching a stopped vehicle in a dangerous position on the road (and if the emergency vehicle positions itself to deliberately move people away from an incident, this is called fend off). Common colours for emergency vehicle warning beacons are blue and red, and this varies by country (and sometimes by operator). The lights can be made to flash via a range of techniques, dependent on the technology used, and the desired end effect. Types of beacon include: Light bars - A long but narrow 'strip' of lights on top of an emergency vehicle, which can be configured with almost infinite combinations of different lighting technologies from the list below. These are typically the main source of flashing light for the vehicle, and are used on overt marked emergency vehicles. They can also be divided into sections, with an array of functions (for instance front blue flashing lights, and rear red flashing lights, switched separately). Due to the nature of the wind resistance encountered by these large