A system comprising an assembly, and a transformer comprising a main housing and at least one primary connector (55, 65), the assembly comprising a first switching device and a second switching device for a vehicle comprising the transformer, the vehicle being in particular a public transport vehicle, each primary connector (55, 65) being configured to be supplied with electricity by the first switching device, the first switching device comprising a first housing, a first input terminal, at least one secondary connector (130, 135) and a first switching member configured to switch between a first configuration, in which the first switching member electrically connects the first input terminal and one of the secondary connectors, and a second configuration, in which the first switching member electrically isolates the first input terminal from said secondary connector, said secondary connector being connected to one of the primary connectors, the first switching member being accommodated in the first housing, the second switching device comprising a second housing, a second input terminal, a tertiary connector and a second switching member configured to switch between a third configuration in which the second switching member electrically connects the second input terminal and the tertiary connector and a fourth configuration in which the second switching member electrically isolates the second input terminal from the tertiary connector, the second switching member being housed in the second housing, the tertiary connector being electrically connected to the second switching member, characterised in that the tertiary connector connected to the first input terminal, one of the secondary connectors (130, 135) being configured to cooperate with one of the primary connectors (55, 65) to securely fix the first switching device to the transformer when said primary connector is connected to said secondary connector (130, 135), the first input terminal being configured to cooperate with the tertiary connector to secure the second switching device to the first switching device in a connection position when the tertiary connector is connected to the first input terminal, the second switching device being integral with the first housing when the second switching device is in its connection position. the first switching device comprising a first housing, a first input terminal, at least one secondary connector (130, 135) and a first switching member configured to switch between a first configuration, in which the first switching member electrically connects the first input terminal and one of the secondary connectors, and a second configuration, in which the first switching member electrically isolates the first input terminal from said secondary connector, said secondary connector being connected to one of the primary connectors, the first switching member being accommodated in the first housing, the second switching device comprising a second housing, a second input terminal, a tertiary connector and a second switching member configured to switch between a third configuration in which the second switching member electrically connects the second input terminal and the tertiary connector and a fourth configuration in which the second switching member electrically isolates the second input terminal from the tertiary connector, the second switching member being housed in the second housing, the tertiary connector being electrically connected to the second switching member, characterised in that the tertiary connector connected to the first input terminal, and a first switching member configured to switch between a first configuration, in which the first switching member electrically connects the first input terminal and one of the secondary connectors, and a second configuration, in which the first switching member electrically isolates the first input terminal from said secondary connector, said secondary connector being connected to one of the primary connectors, the first switching member being accommodated in the first housing, the second switching device comprising a second housing, a second input terminal, a tertiary connector and a second switching member configured to switch between a third configuration in which the second switching member electrically connects the second input terminal and the tertiary connector and a fourth configuration in which the second switching member electrically isolates the second input terminal from the tertiary connector, the second switching member being housed in the second housing, the tertiary connector being electrically connected to the second switching member, characterised in that the tertiary connector connected to the first input terminal, one of the secondary connectors (130, 135) being configured to cooperate with one of the primary connectors (55, 65) to securely fix the first switching device to the transformer when said primary connector is connected to said secondary connector (130, 135), the first input terminal being configured to cooperate with the tertiary connector to secure the second switching device to the first switching device in a connection position when the tertiary connector is connected to the first input terminal, the second switching device being integral with the first housing when the second switching device is in its connection position.