 the same depreciation schedules set by the Internet Revenue Service for tax purposes. [19] The standards committee was accredited by the American National Standards Institute (ANSI), whose naming structure consisted of a letter-number combination; for example, computer language standards were under the X3 committee. "T1" was chosen because it resembled the first two consonants in "telecommunications," not because of the carrier system of the same name. ANSI standards are named for the committee name followed by a number, such as T1.601. [20] Hecht, J., City of Light, Oxford University Press, 1988. [21] Smithsonian Institution, http://www.sil.si.edu/Exhibitions/Underwater-Web/uw-optic- 05.htm. [22] Introduced in the 1990s, the hybrid fiber-coax system used by cable television companies makes use of analog transmission of broadcast video channels over fiber optics. This allows for an inexpensive transition to coaxial cable near the subscribers' locations. Digital cable generally makes use of 6-MHz television channels within that bandwidth, within each of which a modem transmits multiplexed streams of digitized broadcast channels. [23] Even the major carriers quietly resold each other's services; some traded bandwidth for backup purposes, while some rural LATAs were only reachable via AT&T's facilities. It was called synchronous because it assumed that all network elements could synchronize their timing against a single precision reference source. Earlier digital transmission schemes, such as DS3, were designed for digital islands in an analog sea, where there would be considerable variation from nominal transmission speeds. Synchronous opera- tion made multiplexing much simpler. [25] The author also wrote the book ISDN in Perspective, Reading, MA: Addison-Wesley, 1992. In a 1987 article in Trends in Communications Management, he described ISDN as "the invisible elephant," referring to the parable of the blind men and the elephant, and used the same phrase as the title of the book's first chapter. In 1992, along wi