The Emergency Call Box / SOS boxes are mainly used on highways to help the motorists by making their communication easy with the highway authorities when they are in a problem.
The SOS box has a button and when pushed that call is connected to the control room of that particular highway who are further connected to their patrolling vehicles. The motorist informs the control room about the situation he/her is into and gets their solution. The situation can be accident, traffic jam, tyre puncture, no petrol, medical aid, etc
The SOS boxes are connected to the control room via different mediums like wire or wireless. The communication base of the ECB can be Fibre or GSM.