DETAILED DESCRIPTION The present invention overcomes the deficiencies in the art and satisfies this need by providing an ISDN terminal adapter which provides automatic ISDN switch detection, automatic SPID (service profile identification) configuration, baud rate unblocking and automatic data compression.
In accordance with our invention and as to automatic switch detection and SPID configuration, our inventive terminal adapter automatically detects the switch type by analyzing D-channel ISDN initialization messages received from the switch as well as, where appropriate, responses, in terms of D-channel ISDN messages, received from the switch to specific ISDN messages sent by the adapter, and sets the switch type accordingly.
The switch type value is then used, during SPID determination, in conjunction with the directory telephone number of the user, to access an internal database, specifically a table, 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 to which the adapter is likely connected.
Our inventive terminal adapter forms a SPID through interaction among the user; the DTE, such as a personal computer (PC); the terminal adapter and the ISDN switch.
In essence, firmware executing within the terminal adapter, in conjunction with software executing within the PC, forms one of more SPID (s) appropriate for the ISDN switch to which the adapter is connected, queries the switch with each of these SPIDs to select and verify a correct SPID from those formed, and, if necessary, further refines and updates the switch type previously determined.
Furthermore, with respect to baud rate unblocking, our inventive terminal adapter detects instances of baud rate mismatch, through excessive communication errors for a known, e.
g.
, user, input, and forces the adapter to relinquish its fixed speed setting and automatically return to autobaud operation.
As a result, the adapter is then able to match its serial communication speed with that of the DTE, e
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Multiplexer-related 
