(emergency brake) The MI 79 (French: Matériel d'Interconnexion de 1979, English: interconnection rolling stock of 1979), also known as the Class Z 8100 is a dual-voltage electric multiple unit trainset that is operated on line B of the Réseau Express Régional (RER), a hybrid suburban commuter and rapid transit system serving Paris and its suburbs.

In the early 1970s, work was underway to create the Réseau Express Régional (RER), a hybrid suburban commuter and rapid transit system serving Paris and its suburbs.

The Ligne de Sceaux to south of Paris, owned by RATP, had 1.5 kV DC electrification and platforms at a height of 105 cm (41 in), while the Chemin de Fer du Nord to the north of Paris, owned by SNCF had 25 kV AC electrification and platforms at a height of 55 cm (22 in).

The retirement of the Z 23000 railcars dating from 1938 was postponed to make up for the shortfall in equipment caused by MI 79 trainsets sidelined with frost issues.

Also, because the RER B would serve Charles de Gaulle Airport, trains were equipped with luggage racks above the seats.

When in use, they obstruct part of the entryway, leaving a space only 40 centimetres (16 in) wide for passengers to board or disembark.

Designated the EHO 3262 A, these direct current (DC) motors are cooled by air and each develops 310 kW (420 hp).

The €274.75 million project included a technical update, installation of refrigerated ventilation, and changes to the interior layout of the cars.

One major change was the elimination of the overhead luggage shelves which prevented heating and ventilation ducts from being installed on the ceiling of the cars and were only lightly used by passengers.

A passenger information system (SISVE) was also installed, which provides audio announcements and visual display of the trains next stop with available connections.