An electronic milbus repeater circuit for expanding the capacity of a two-wire bus used for the transmission of data. By means of logic circuitry of the Milbus repeater according to the invention, data received by the Milbus repeater is distributed between the secondary Milbus and the Milbus repeater's own internal bus according to the coded address and subaddress of each data transmission.

A ring-shaped data communications network in which plural slave stations and a master station are serially connected in a closed loop via transmission lines, the slave stations being removably connected to the loop without affecting the continuity of data transmission on the loop. A connection box, permanently connected into the loop and adapted to receive the removable slave station, has circuitry for switching the data loop paths through the slave station. Switching of the data loop occurs when the slave station has been physically connected to the connection box and when a non-communicating portion of the data stream in the loop has been received at the connection box. Apparatus for detecting the connection of the slave station to the box and for detecting the absence of information in the data stream controls operation of the switching.

An optical bypass switch for a fiber optic local area communications network (LAN) with a ring topology allows an optical signal carried on the ring to by pass a node, which includes terminal equipment and a stub cable, associated with the switch. In a non-bypass mode, the optical signal is transmitted to and from the associated terminal. The switch assembly is remote from its associated terminal and includes optical couplers and associated optical receivers and activity detectors to produce electrical signals indicative of an optical input to and output from the terminal. Logic circuitry analyzes these signals and produces an appropriate drive signal for a switch controller. The remote switch has a local power supply and is preferably located at the junction of the ring and an associated, purely dielectric stub cable. The terminal can include a dual path transceiver and bridging equipment to provide cross links between terminals in the event of a link failure to complement the node failure protection of the bypass switch.

A live insertion and removal mechanism assures that a sub-assembly being inserted or removed from a live electronic assembly does not disrupt system power and buses and is protected against the negative affects of current surge. An active current control device and related circuitry, and a connector having a plurality of graduated pin lengths effect a controlled ramp-up and ramp-down of power to the sub-assembly inserted into and removed from the live electronic assembly. Additionally, means are provided for effectively disconnecting selected output drivers from signal and control paths to avoid damage to the drivers upon insertion or removal of the sub-assembly from the live assembly.

A live insertion and removal mechanism assures that a sub-assembly being inserted or removed from a live electronic assembly does not disrupt system power and buses and is protected against the negative effects of current surge. An active current control device and related circuitry, and a connector having a plurality of graduated pin lengths effect a controlled ramp-up and ramp-down of power to the sub-assembly inserted into and removed from the live electronic assembly. Additionally, disconnecting selected output drivers from signal and control paths to avoid damage to the drivers upon insertion or removal of the sub-assembly from the live assembly.