3Com Corporation

Leming Xu

Meir Dahan

Scott C Herschler

An analog subscriber unit adapter/interface which generates a low voltage ring-tone signal to an audio speaker is provided The adapter facilitates the use of an analog subscriber unit over an ISDN communications link and provides added functionality to ISDN devices. The SLIC simulator interface of the present invention is preferably provided as part of an ISDN modem, thereby giving added functionality to the modem by allowing analog phones to operate over an ISDN line. The interface operates by simulating the services and functions of an analog SLIC (Subscriber Line Interface Circuit) while converting and formatting the analog information to an ISDN compatible form, and vice versa. The SLIC simulator provides an audible ring-tone signal indicative of an incoming call by way of an audio speaker, thereby obviating the need for a high amplitude ring voltage signal to be sent to the subscriber unit. The need for a ring-trip circuit is therefore also obviated. The absence of a high amplitude ring voltage also permits circuit simplification and associated cost savings because the electrical isolation requirements recognized in the telecommunications industry are less strict for low-voltage circuits.

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Skokie, IL, United States of America

Leming Xu