Abstract: In the modem based data transmission system the transmitting section provides a bit from each terminal (DTE) to be stored into a transmission buffer register (BX) under the control of an external clock signal derived from a modem internal transmission clock signal. The contents of the transmission buffer register is transferred into a transmission shift register and then transferred toward the modem through a formatting logic circuit wherein so-called stuffing bits and synchronization or flag characters are being inserted. Opposite operations are performed in the receiving section of the data transmission system.

Abstract: The structure described is a switching-processing node for high speed data transmission systems. Information is transmitted in time slot channels, one of which is control information. Data to be passed through a node is stripped of control characters, passed to a transmitting unit and there re-encoded with such additional data bits as needed. Data for the node is switched from an input decoder to a processor input and data for transmission is switched to a transmission unit for encoding.A switching information control frame can be passed over the system to set the switching circuits at a node to operate at the appropriate time slots of the data frames.