Concentrator

The utility model relates to an extension communication equipment field especially relates to a concentrator. The utility model discloses a concentrator, it includes an output port, the 2nd output port, host processing ware and at least one input port, a host processing ware one end and an output port and the 2nd output port pass through mutually independent circuit connection respectively, one end is connected with at least one output port, an output port is different with the 2nd output port's type, an output port and the 2nd output port are used for being connected with upper link device, input port is used for being connected with second line of a couplet equipment, when an output port or the 2nd output port are connected with upper link device, whether the circuit that the host processing ware detected an output port or the 2nd output port place has the circular telegram, there is the circular telegram then to keep this alive circuit intercommunication if detect one of two circuit, otherwise switch to an