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MILESTONES IN DIGITAL TELEPHONY

This is a highly compressed list of milestones in digital telephony, in roughly chronological order. This should be expanded into a fully developed article

  • early experiments with Pulse Code Modulation in telephony

  • the 8-bit, 8kHz standard is developed; Nyquist's Theorem and the standard 3.5kHz telephony bandwidth

  • DS0 as the basic digital telephony bitstream standard

  • vs. μ-law , and transcoding between the two

  • Bit Error Rate and intelligibility

  • first practical digital telephone systems put into service

  • the U.S. T-carrier system and the European E-carrier system developed to carry digital telephony

  • introduction of Space-time Switching in fully digital Electronic Switching System s

  • replacement of tone signaling with digital signaling for trunks

  • In-band Signaling vs. Out-of-band Signaling

  • the problem of Bit-robbing

  • development of SS7

  • emergence of Fiber Optic Network ing allows greater reliability and call capacity

  • transition from Plesiochronous transmission to synchronous systems like SONET / SDH

  • optical Self-healing Ring networks further increase reliability

  • digital/optical systems revolutionize international long-distance networks, particularly undersea cables

  • digital telephone exchanges eliminate moving parts, make exchange equipment much smaller and more reliable

  • separation of exchange and concentrator functions

  • roll-out of digital systems throughout the PSTN

  • provision of Intelligent Network services

  • digital Speech Coding and compression

  • speech compression on international digital trunks

  • Phone Tapping in the digital environment

  • introduction of digital mobile telephony, specialized compression algorithms for high Ite Error Rate s

  • direct digital termination to customers via ISDN ; PRI catches on, BRI mostly does not, except in Germany

  • the effects of digital telephony, and digital termination at the ISP, on modem performance

  • Voice Over IP as a carrier strategy

  • emergence of ADSL leads to voice over IP becoming a consumer product, and the slow demise of dial-up Internet access

  • expected convergence of VoIP , mobile telephony, etc.

  • flattening of Telephony Tariff s, increasing moves towards Flat Rate pricing as the Marginal Cost of telephony drops further and further



SEE ALSO



FURTHER READING

  • John Bellamy. ''Digital Telephony'' (3rd Edition, 2000).