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digital cross-connect

A network device used by telecom carriers and large enterprises to switch and multiplex low-speed voice and data signals onto high-speed lines and vice versa. It is typically used to aggregate several T1 lines into a higher-speed electrical or optical line as well as to distribute signals to various destinations; for example, voice and data traffic may arrive at the cross-connect on the same facility, but be destined for different carriers. Voice traffic would be transmitted out one port, while data traffic goes out another.

Cross-connects come large and small, handling only a few ports up to a few thousand. Narrowband, wideband and broadband cross-connects support channels down to DS0, DS1 and DS3 respectively.

Used With Telephone Switches
Digital cross-connects (DCSs) are widely used in conjunction with central office telephone switches and may be installed both before and/or after the switch. Cross-connections are established via an administrative process and are semi-permanent, whereas the telephone switch dynamically picks up dialing instructions and routes calls based on telephone number. See optical cross-connect.




A Digital Cross-Connect (DCS)
Digital cross-connects come in many sizes and can take up as little as one shelf on a rack or as many as 60. This TITAN 5500 system from Tellabs is an example of a large wideband cross-connect. (Image courtesy of Tellabs.)









Telco Switch Entry Points
The digital cross-connect (DCS) serves as the entry/exit point on the trunk side of the switches in local telephone company central offices as well as the wire centers of the interexchange carriers (IXCs).






optical cross-connect

A network device used by telecom carriers to switch high-speed optical signals (OC-3, OC-12, OC-48, etc.). It differs from a digital cross-connect in that it deals with multiple high-speed signals that are switched in their entirety and not multiplexed together.

Also known as "OXCs," optical cross-connects work entirely at the optical layer and may be able to operate without having to convert to electrical and back again. Tellium, Inc., a Bellcore spin-off acquired by Zhone Technologies (www.zhone.com) in 2003, introduced the first optical cross-connect in 1998. See digital cross-connect.



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