Grandfathered system
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Grandfathered systems: Telecommunication systems that include, but not limited to:
(a) PBX and key telephone systems, directly connected to the public switched telephone network on June 1, 1978, that may remain permanently connected thereto without registration unless subsequently modified, and
(b) systems that are of the same type as those connected to the public switched telephone network on July 1, 1978, that were added before January 1, 1980, and that may remain permanently connected thereto without registration unless subsequently modified.
This article contains material from the Federal Standard 1037C, which, as a work of the United States Government, is in the public domain.
