Editing Digital Signal 1 (section)

==Alternative technologies==
'''Dark fiber''': ''[[Dark fiber]]'' refers to unused [[Optical fiber|fibers]] available for use. Dark fiber has been, and still is, available for sale on the wholesale market for both metro and wide area links, but it may not be available in all markets or city pairs.

Dark fiber capacity is typically used by network operators to build [[SONET]] and [[dense wavelength-division multiplexing]] (DWDM) networks, usually involving meshes of [[self-healing rings]]. Now, it is also used by end-user enterprises to expand [[Ethernet]] local area networks, especially since the adoption of [[IEEE]] standards for [[gigabit Ethernet]] and [[10 Gigabit Ethernet]] over single-mode fiber. Running Ethernet networks between geographically separated buildings is a practice known as "[[Wide area network|WAN]] elimination".

'''DS1C''' is a digital signal equivalent to two ''Digital Signal 1'' circuits, with extra [[bit]]s to conform to a signaling standard of 3.152&nbsp;Mbit/s. Few (if any) of these circuit capacities are still in use today. In the early days of digital and data transmission, the three-megabit-per-second data rate was used to link [[mainframe computers]] together. The physical side of this circuit is called T1C.<ref>{{cite book|title=Microsoft Encyclopedia of Networking, Second Edition|date=24 April 2002|last1=Tulloch|first1=Mitch|last2=Tulloch|first2=Ingrid}}</ref>