This multifrequency device (10) is configured to be connected via at least two conductors (121, 122) to an electricity supply grid (11). This device comprises: at least one radiofrequency module (13) comprising at least one first and one second input/output port (131, 132), which ports are able to emit and/or receive radiofrequency signals at two different frequencies; and at least two matching circuits (14, 15) that are configured to block the propagation of radiofrequency signals propagating over the conductors, each matching circuit comprising a plurality of terminals. One terminal (141, 151) of each matching circuit is connected to the first conductor or to the second conductor. One terminal (142, 151) of each matching circuit is connected to the first input/output port or to the second input/output port of the radiofrequency module. This device also comprises decoupling means (C1, C2) that are configured to stop the propagation of electrical supply signals between the conductors and between at least one conductor and an input/output port of the radiofrequency module.