Material relates to the critical issue of MCI business in the 1970's - interconnection with AT&T's telecommunication network in order to provide private line services nationwide. HBP participated in all the aspects of negotiations, regulatory and legal battles on the issue and accumulated great deal of correspondence, pleadings with FCC by MCI, AT&T and other participating parties, and supporting documents. Folders include material relating to the Carterphone Decision [June 1968] in which FCC permitted connection of customer-owned equipment to the public telephone system; AT&T's new tariffs for the interconnection [Foreign Attachment tariffs Nos. 263, 260 and 259]; companies', including Microwave Communications Inc., pleadings with FCC and correspondence with Common Carrier Bureau regarding these tariffs; documents on technical issues of interconnection; MCI's correspondence with AT&T and Bell Companies regarding connection of its customers to local facilities; drafts of agreements for local interconnection between MCI and Bell Companies [starting July 1973, the term interconnection was changed to Expanded Service Agreements (ESA)]; MCI local loop requests from Southwestern Bell and Illinois Bell telephone companies; material concerning the FCC meeting on technical matters involving interconnection, September 12, 1972; correspondence, notes and statements on MCI's policy relating to other common carriers; memoranda regarding particular problems with interconnection.