Patent ID: 7133357

Claim:
A transmitter comprising: a first cell switch module placeable in either an active state or a standby state, and including a plurality of first input ports for inputting cells thereto respectively, and a plurality of first output ports for outputting cells therefrom respectively; a second cell switch module placeable in either a standby state or an active state inversely to said first switch module, and including a plurality of second input ports for inputting cells thereto respectively, and a plurality of second output ports for outputting cells therefrom respectively; a plurality of first physical lines connected respectively to the corresponding first input ports and second input ports; a plurality of second and third physical lines connected respectively to the corresponding first output ports and second output ports; a plurality of selectors for selecting, in response to a select signal, either one signal out of the signals inputted from the two second and third physical lines corresponding to each other; and switching control means for generating said select signal to instruct said selector to execute active/standby switching: wherein each of said first and second cell switch modules comprises a buffer memory for storing the switched cells therein; cell cross-connect means for routing the cells obtained from the input ports, then writing the cells successively in the relevant buffer memory; cell switching control means for controlling the switching in such a manner that, in response to an active/standby switching instruction, a decision is made as to whether each cell obtained from the input port is a specific first cell or not, and if the result of such decision signifies that the cell is said specific first cell in the active state, any subsequent cell obtained thereafter from the input port is not switched by said cell cross-connect means, but if the cell is said specific first cell in the standby state, any subsequent cell obtained thereafter from the input port is switched by said cell cross-connect means; cell reading control means for successively readings in the active state, the cells written in said buffer memory; and queue empty detection means for detecting, in the active state, if the all cells written in said buffer memory have been completely read out therefrom: wherein said switching control means generates the select signal in accordance vith the detection result obtained from said queue empty detection means.