Riot control refers to the measures used by police, military, or other security forces to control, disperse, and arrest people who are involved in a riot, demonstration, or protest. If a riot is spontaneous and irrational, actions which cause people to stop and think for a moment (e.g. loud noises or issuing instructions in a calm tone) can be enough to stop it. However, these methods usually fail when there is severe anger with a legitimate cause, or the riot was planned or organized. Law enforcement officers or military personnel have long used less lethal weapons such as batons and whips to disperse crowds and detain rioters. Since the 1980s, riot control officers have also used tear gas, pepper spray, rubber bullets, and electric tasers. In some cases, riot squads may also use Long Range Acoustic Devices, water cannons, armoured fighting vehicles, aerial surveillance, police dogs or mounted police on horses. Officers performing riot control typically wear protective equipment such as riot helmets, face visors, body armor (vests, neck protectors, knee pads, etc.), gas masks and riot shields. However, there are also cases where lethal weapons are used to violently suppress a protest or riot, as in the Boston Massacre, Haymarket Massacre, Banana Massacre, Hungarian Revolution of 1956, Kent State Massacre, Soweto Uprising, Mendiola Massacre, Bloody Sunday (1972) and Tiananmen Square Massacre.