Maitrise Technologique E.R.N system is intended to treat any emergency call from emergency roadside telephones functioning according to different technologies like GSM, Ethernet, fiber optics or telephony. Its complex general architecture allows the management of motorways network until 5 000 km with 1 to 100 operators to receive the calls. It supplies security and functioning safety at the road user. The guarantee of service to the user in distress is provided by redundant hardware. It is based on IHM921, PIRAU IP and Emergency Roadside Telephone equipment.