Abstract: An arrangement whereby a passive line concentrator (100) can be connected in a managed token ring network includes a special concentrator port (200) in an active concentrator (10) which is adapted to have inserted the ring-in port (130) of the passive line concentrator. The special concentrator port of the active concentrator supplies a small phantom current to the passive concentrator, which returns the phantom current only if it has at least one active port. Detection of the returned phantom current controls insertion of the special concentrator port into the network.

Abstract: A concentrator for a token ring network utilizes latching relays having separate set and reset coils for controlling the insertion/bypass of the ports into the token ring network. Circuitry for providing a global reset capability for all of the ports includes transistors which function to both provide a path for the global reset pulse to the reset coils and to isolate each reset coil in a port from the reset coils of the other ports. Other circuitry is provided for preventing activation of the global reset function from affecting an active port.