Communication unit for equipping an aircraft communication network, characterised in that it has at least one output (14a; 114a) intended to be connected to at least one receiver and at least first and second inputs (6a, 10a; 106a, 110a) intended to be connected to two sources of signals of a first type (BLACK) and a second type, respectively, the unit defining areas electromagnetically isolated from one another, including: - a first area (3; 103) having a first transmission channel (7; 107) for transporting the signals of the first type, a first selector (8; 108) being disposed between the first input and the first transmission channel to place the first transmission channel either in an active state in which it is connected to the first input to transport the signals from the first input or in a passive state in which it is isolated from the first input and prevented from transmitting; - a second area (4; 104) having a second transmission channel (11; 111) for transporting the signals of the second type, a second selector (12; 112) being disposed between the second input and the second transmission channel to place the second transmission channel either in an active state in which it is connected to the second input to transport the signals from the second input or in a passive state in which it is isolated from the second input and prevented from transmitting; - a third area (5; 105) to which the first and second transmission channels lead and having a third transmission channel connected to the output of the switch, a third selector (15; 115) being disposed between the third transmission channel and the first and second output channels to connect the third transmission channel selectively to the first transmission channel or to the second transmission channel, the selectors being associated with simultaneous control means (18; 118) so that when one of the first or second transmission channels is in an active state and is connected to the third transmission channel the other of the first or second transmission channels is in a passive state. - a first area (3; 103) having a first transmission channel (7; 107) for transporting the signals of the first type, a first selector (8; 108) being disposed between the first input and the first transmission channel to place the first transmission channel either in an active state in which it is connected to the first input to transport the signals from the first input or in a passive state in which it is isolated from the first input and prevented from transmitting; - a second area (4; 104) having a second transmission channel (11; 111) for transporting the signals of the second type, a second selector (12; 112) being disposed between the second input and the second transmission channel to place the second transmission channel either in an active state in which it is connected to the second input to transport the signals from the second input or in a passive state in which it is isolated from the second input and prevented from transmitting; - a third area (5; 105) to which the first and second transmission channels lead and having a third transmission channel connected to the output of the switch, a third selector (15; 115) being disposed between the third transmission channel and the first and second output channels to connect the third transmission channel selectively to the first transmission channel or to the second transmission channel, the selectors being associated with simultaneous control means (18; 118) so that when one of the first or second transmission channels is in an active state and is connected to the third transmission channel the other of the first or second transmission channels is in a passive state.