Abstract: A method and apparatus for discerning between unknown but standardized ISDN interfaces, such as the U and S/T reference points, and automatically selecting compatible routing for the respective interface to compatible ISDN equipment. An unknown reference point supported by an ISDN service provider is interfaced with a reference adaptor comprised of an interface selection circuit which discerns the standardized form of the unknown reference point presented by the service provider and appropriately switches a relay means for routing the unknown interface reference point to ISDN equipment, either directly or indirectly through a transformation NT-1 device. Protection circuitry prevents signals from one reference interface from damaging sensitive circuitry of another reference interface.

Abstract: An apparatus and method for facilitating interaction during a communication session between an analog modem and a terminal adapter for conveying digital alert tones and control data therebetween is provided. The embodiments provide for a collateral digital communication path between a microcontroller of an analog modem and a microcontroller of a terminal adapter for selectively relaying digital alert tones and control data therebetween. One embodiment utilizes a cellular interface of an analog modem for tapping and evaluating information for the presence of control data. Upon successful identification of control data, the microcontroller of a terminal adapter is notified and the specific control data detected in identified. By providing a method of apparatus for digitally relaying control data, accuracy of identification of control data by a terminal adapter is enhanced by foregoing needless signal transformation and retransformation.