Conformance with established standards and interoperability between products in an integrated services digital network (ISDN) system defined by a layered hierarchy of interrelated protocols is ascertained by remotely testing the protocols between a tester in a local testing centre and a system under...http://www.google.ca/patents/US5027343?utm_source=gb-gplus-sharePatent US5027343 - Remote test access system for ISDN testing
