| 摘要 |
<p>Apparatus for an improved ISDN terminal adapter (5) and accompanying methods for use therein. The adapter provides automatic ISDN switch detection, automatic SPID configuration, baud rate unblocking and automatic data compression. Specifically, the adapter automatically detects a type of ISDN switch (480) to which the adapter is connected by analyzing D-channel initialization messages which are received by the adapter from the switch as well as specific responses to ISDN messages sent by the adapter. The switch type value is then used, during SPID determination, in conjunction with a telephone area code of the user, to access an internal database (435) of predefined SPID formats, referenced in terms of particular telephone service areas and switch types, to access the possible SPID format(s) for the ISDN switch. Firmware (460) executing within the DTE, forms one of more SPID(s) appropriate for the switch, queries the switch with each of these SPIDs to select and verify a correct SPID from those formed, and, if necessary, further refine and update the switch type previously determined. As to baud rate unblocking, the adapter detects instances of baud rate blocking, through excessive communication errors for a known input, and forces the adapter to relinquish its high speed setting and automatically return to autobaud operation but at a lower maximum speed. The adapter also automatically provides B-channel data compression in the event the DTE is unwilling or unable to do so. Here, the adapter monitors negotiation, over an ISDN line, of a compression control protocol (CCP) between the DTE and far-end equipment (5', 1130). If the negotiations reveal that the DTE will not undertake compression, then the adapter will then automatically negotiate the protocol and thereafter, for the duration of a call, perform compression and decompression in lieu of the DTE.</p> |
