Patent ID: 7912096

Claim:
An add/drop multiplexer for connection between a first network, on which first low-order group signals are transferred at a predetermined speed, and a second network, on which high-order group signals are transferred at a higher speed than that of the first low-order group signals, said multiplexer comprising: (a) a cross-connect for handling cross-connecting of signals to be transferred between the first and second networks in terms of second low-order group signals whose transmission speed is slower than that of either the high-order group signals or the first low-order group signals; and (b) an interface for handling signal transfer to and from said cross-connect in terms of the high-order group signals; said interface including (b1) a first signal converter for converting inputted first low-order group signals into high-order group signals, which are to be transferred to the second network and to which second low-order group signals slower in transmission speed than that of the first low-order group signals are multiplexed, and outputting the resulting high-order group signals to said cross-connect, (b2) a second signal converter for converting high-order group signals, which are received from the second network via said cross-connect, into first low-order group signals, and (b3) a selector for selectively outputting the first low-order group signals, which are received from the first network, or the first low-order group signals, which are obtained by said second signal converter, as last-named input signals to said first signal converter.