A device has a host port, a remote terminal (RT), an incoming line driver, an outgoing line driver, and at least one of an incoming message filter and an outgoing message filter. The host port communicatively couples to a shared host bus. The RT port communicatively couples to the RT. The incoming message filter receives an incoming host message from the host port and generates a filtered host message from the incoming host message employing at least one host message rule. The outgoing message filter receives an outgoing RT message from the RT port and generates a filtered RT message from the outgoing RT message employing at least one RT message rule. The incoming line driver communicates the filtered host message to the RT port. The outgoing line driver communicates the filtered RT message to the host port.