Hayes Microcomputer Products, Inc.

Ascend Communications, Inc.

Stephen J Speckenbach

Jay P Duncanson

An apparatus and a method for use in a digital communication session is disclosed. The apparatus communicates with a like apparatus at a remote location through a digital communication network over a plurality of channels. The apparatus can change dynamically the bandwidth of the communication session by changing the number of channels utilized during the communication session. In addition, the apparatus provides a novel phase correction circuitry for reordering the digital data received from the plurality of channels to reconstitute the single transmitting digital data stream.

Method and apparatus for digital communication

A speed correction circuit for use in a modem implementing a data communications protocol having tighter tolerances on bit timing for the transmitted data than for the input data. Selective insertion and deletion of stop bits is used to compensate for overspeed or underspeed conditions between the input and the transmitted data streams. The apparatus loads the incoming data into a FIFO register of predetermined length. Counters in a clock circuit keep track of character timing. Just before transmission of a stop bit, predetermined positions in the FIFO are tested to see if they are occupied in order to detect an overspeed or underspeed condition. If no overspeed or underspeed is detected the top bit is transmitted in its normal fashion. If underspeed is detected, a transmit controller sends a stop bit, and shifting out of the last bit in the FIFO is suppressed for one bit time. This inserts a stop bit in the data stream while allowing additional bits to come into the FIFO. If overspeed is detected, the stop bit then present at the output of the FIFO is shifted out prior to the transmit controller being clocked to send out the bit then present on the FIFO output. This shifts out the stop bit and allows the first bit from the next character to ripple through to the output prior to clocking of the transmit controller, thus deleting a stop bit from the transmitted data stream to correct the overspeed condition.

Speed correction and stop bit control circuit for data communications

A method and apparatus for allowing ISDN devices to communicate over an analog telephone line is shown. A first interface (12) accepts ISDN formatted data from an ISDN terminal equipment (TE) device (10), removes the D channel data from the ISDN data, and provides the D channel data to a synchronous modem (14). The modem (14) places onto an analog telephone line (15) a modulated carrier corresponding to the D channel data. The modulated carrier is passed through a telephone switch (16)onto another analog telephone line (17). A second synchronous modem (20) accepts the modulated carrier, demodulates the modulated carrier to recover the data, and provides the data to a second interface (22). The second interface (22) accepts the data from the modem (20), inserts the data into the D channel information in ISDN data stream, and provides the ISDN data stream to an ISDN network termination (NT) device or ISDN switch (24). The result is that two ISDN devices can communicate with each other, even in areas where the local telephone company does not provide ISDN capability and the two devices must communicate with each other using a non-ISDN medium, such as an analog telephone line. Furthermore, an ISDN device can be tested and evaluated for compatibility and operation with ISDN switch without the necessity of having to transport the ISDN device to an area wherein the local telephone company provides ISDN switching capabilities.

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Oakland, CA, United States of America

Stephen J Speckenbach