Abstract: An ATM cell transferred from a first ATM node to a second ATM node is, in a normal state, transmitted to a line control unit from an ATM cell switch within the first ATM node and sent to a trunk line therefrom. when a usage of a buffer connected within this line control unit comes to a fixed threshold value or larger, in the line control unit for sending the ATM cell to the ATM cell switch, routing (TAG) data added to a header part of the ATM cell belonging to a low-quality connection among connections directed to the second ATM node is so rewritten as to be directed to the line control unit. The relevant cell is sent forward to the line control unit and transferred to the second ATM node via a backup line.

Abstract: An ATM switching system has a receiving unit for receiving an ATM cell, reassembling it into a frame and temporarily storing a buffer memory with this frame. When the receiving unit receives the cell, there is discriminated whether the cell is a continuous in-receipt cell or a last cell. A cell-to-cell receiving time or a receiving time between a head cell and the last cell is monitored. When this receiving time exceeds a set time, a determination is that the cell loss is detected. Invalid holding of a buffer memory is restrained by releasing the buffer memory.

Abstract: A digital-transmission/analog-transmission changeover apparatus in a communication system for performing a digital transmission between a digital terminal and a terminal accommodated by an ISDN, and performing an analog transmission via the ISDN and an analog network, between the digital terminal and a terminal accommodated by the analog network includes a rate converter for converting the rate of data, which has entered from the digital terminal, to a rate suited to the ISDN, and for converting the rate of data, which has entered from the ISDN, to the rate of the digital terminal. A modulator/demodulator for modulating digital data, which has entered from the digital terminal, into an analog signal and demodulating the analog signal into digital data is provided. A PCM converter is connected to the modulator/demodulator for converting the analog signal into digital data at a rate suited to the ISDN, and converting digital data from the ISDN into the analog signal.

Abstract: A remote maintenance ATM cell transmitted from a remote maintenance terminal is input to a channel control section of a node. An ATM cell header fast transform circuit affixes routing information indicating that a control signal transmitter/receiver section is the destination to the header portion of the remote maintenance ATM cell, and updates VPI/VCI values with values indicating a channel through which the ATM cell is transmitted. Then, the remote maintenance ATM cell is transmitted through an ATM cell switch to the control signal transmitter/receiver section. The remote maintenance ATM cell is formed into a frame there, which is transferred to a main control section. The main control section controls the individual sections of the node based on the received frame.