In 1957, when digital systems were first proposed and developed, the boss decided to skip Q, R, S, and to use T, for Time Division. The idea was this will be the world's first time division system. Vaiants of T1, called T1C, T2, T3, and T4, all died. They are survived by signals that would have been carried on all these systems, called DS1, DS2, DS3, and DS4. Among the successor to T1 vying for success at Bell Labs, digital coaxial cables, digital microwave, satellite, circular waveguide, optical mirror, and optical fiber, none achieved commercial success save fiber.
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