Abstract: A large number of local area networks are each connected to a backbone network through a network interface module (NIM). The NIM transmits messages from one local area network to another local area network across the backbone network by enveloping the local area network message inside the data field of a backbone network message. Each of the NIM constructs a table of addresses. The backbone network messages are each addressed to the particular destination NIM. The destination NIM receives the backbone network message and de-envelopes it for transmission over its own local area network.

Abstract: Disclosed is a unit for interfacing an 82586-type local-communications controller to a modem of the type used in an RF network, the unit employing both an NRZI-to-NRZ converter which includes an algorithmic-state machine for converting packets encoded in NRZI format to NRZ format and for recovering the clocking information and a comparator for comparing successive check-sum portions derived from a packet for transmission in the network with similar portions derived from an echo packet received from the network to detect a packet collision.

Abstract: A multiple channel communications system and method for communication among multiple channels using a channel selectable MODEM. The system is comprised of a coaxial cable, a variety of interface units with attached communicating devices and a channel bridge. The interface units include a MODEM and a microprocessor based support element adapted for the attached communicating device. The channel bridge includes two or more .[.MODEM's.]. .Iadd.MODEMs .Iaddend.and a microprocessor based computer for receiving data from one MODEM and transmitting the data on another MODEM.