Abstract: A line driver for a cable linked LAN maintains a high impedance across the cable when not sending data. A pulse transformer includes a primary and secondary winding. The primary winding of the transformer is placed between a first pair of transistors and a second pair of transistors. An array of switching inverters activates these transistors in such a manner whereby, when one pair is turned on, the other pair is turned off. This "off" and "on" toggling of the transistor pairs drives current into the transformer primary. Such current induces a pulse in the transformer secondary which is coupled into the LAN cable.

Abstract: A controller is disclosed for use in a local area network preferably of the type having a token-passing protocol. The controller modifies the contents of a data packet or message as it moves on the network media, thereby to intercept, modify and redirect the data message to nodes other than the originally addressed node. In accordance with one embodiment of the invention, the controller is associated with a high-information node (e.g., a file server) connected in a network with a plurality of low-information nodes. The controller modifies the token address transmitted with the token packet from the high-information node after a number of data transmissions so that the token rather than being passed to the next node is returned to the high-information node, thereby allowing a plurality of successive data transmissions to be made in succession from the high-information node to one or more of the low-information nodes.