An interface device for interfacing between a networkable device such as a
printer and a network, includes a hub and a circuit board, with the hub
constructed with plural ports to repeat network transmissions received on
one port to all other ports. An isolation switch is provided for
controllably isolating the port to which the network is connected so that
network transmissions are not repeated by the hub. The isolation switch
is operated under control of the circuit board, which implements network
functionality for the networkable device. For example, where the
networkable device is a printer, the extended network functionality
provided by the circuit board may relate to secure printing. The
isolation switch can be operated so as to isolate the network from the
printer, to permit the circuit board to transmit decrypted print jobs in
clear text to the printer without danger of interception over the
network.