Communication apparatus comprising: first and second inputs (62, 64), coupled respectively to receive communication signals from first and second stations (22, 32); and first and second outputs (66, 68), coupled respectively to convey the received communication signals to the first and second stations; a single one-way link, which is physically capable of carrying the communication signals in one direction and incapable of carrying signals in the other, opposite direction; and a pair of switches (48, 50), which are coupled to the one-way link and are configured to be toggled between at least a first configuration, in which the communication signals are conveyed from the first input via the single one-way link to the second output, and a second configuration, in which the communication signals are conveyed from the second input via the single one-way link to the first output, characterized in that the pair of switches (48, 50) comprises: a first double-pole switch, which is coupled between the first and second inputs (62, 64) and a transmit side of the single one-way link and is configured to select the first input for connection to the transmit side of the single one-way link in the first configuration and to select the second input for connection to the transmit side of the single one-way link in the second configuration, and a second double-pole switch, which is coupled between the first and second outputs (66, 68) and a receive side of the single one-way link and is configured to select the second output for connection to the receive side of the single one-way link in the first configuration and to select the first output for connection to the receive side of the single one-way link in the second configuration. first and second inputs (62, 64), coupled respectively to receive communication signals from first and second stations (22, 32); and first and second outputs (66, 68), coupled respectively to convey the received communication signals to the first and second stations; a single one-way link, which is physically capable of carrying the communication signals in one direction and incapable of carrying signals in the other, opposite direction; and a pair of switches (48, 50), which are coupled to the one-way link and are configured to be toggled between at least a first configuration, in which the communication signals are conveyed from the first input via the single one-way link to the second output, and a second configuration, in which the communication signals are conveyed from the second input via the single one-way link to the first output, characterized in that the pair of switches (48, 50) comprises: a first double-pole switch, which is coupled between the first and second inputs (62, 64) and a transmit side of the single one-way link and is configured to select the first input for connection to the transmit side of the single one-way link in the first configuration and to select the second input for connection to the transmit side of the single one-way link in the second configuration, and a second double-pole switch, which is coupled between the first and second outputs (66, 68) and a receive side of the single one-way link and is configured to select the second output for connection to the receive side of the single one-way link in the first configuration and to select the first output for connection to the receive side of the single one-way link in the second configuration. a first double-pole switch, which is coupled between the first and second inputs (62, 64) and a transmit side of the single one-way link and is configured to select the first input for connection to the transmit side of the single one-way link in the first configuration and to select the second input for connection to the transmit side of the single one-way link in the second configuration, and a second double-pole switch, which is coupled between the first and second outputs (66, 68) and a receive side of the single one-way link and is configured to select the second output for connection to the receive side of the single one-way link in the first configuration and to select the first output for connection to the receive side of the single one-way link in the second configuration.