A digital cross-connect system (DCS or DXC) is a piece of circuit-switched

Circuit switching

Circuit switching is a methodology of implementing a telecommunications network in which two network nodes establish a dedicated communications channel through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the...

 network equipment, used in telecommunications networks, that allows lower-level TDM

Time-division multiplexing

Time-division multiplexing is a type of digital multiplexing in which two or more bit streams or signals are transferred apparently simultaneously as sub-channels in one communication channel, but are physically taking turns on the channel. The time domain is divided into several recurrent...

 bit streams, such as DS0 bit streams, to be rearranged and interconnected among higher-level TDM signals, such as DS1

Digital Signal 1

Digital signal 1 is a T-carrier signaling scheme devised by Bell Labs. DS1 is a widely used standard in telecommunications in North America and Japan to transmit voice and data between devices. E1 is used in place of T1 outside North America, Japan, and South Korea...

 bit streams. DCS units are available that operate on both older T-carrier

T-carrier

In telecommunications, T-carrier, sometimes abbreviated as T-CXR, is the generic designator for any of several digitally multiplexed telecommunications carrier systems originally developed by Bell Labs and used in North America, Japan, and South Korea....

/E-carrier

E-carrier

In digital telecommunications, where a single physical wire pair can be used to carry many simultaneous voice conversations by time-division multiplexing, worldwide standards have been created and deployed...

 bit streams, as well as newer SONET/SDH

Synchronous optical networking

Synchronous Optical Networking and Synchronous Digital Hierarchy are standardized multiplexing protocols that transfer multiple digital bit streams over optical fiber using lasers or highly coherent light from light-emitting diodes . At low transmission rates data can also be transferred via an...

 bit streams.

DCS devices can be used for "grooming

Traffic grooming

Traffic grooming is the process of grouping many small telecommunications flows into larger units, which can be processed as single entities. For example, in a network using both time-division multiplexing and wavelength-division multiplexing , two flows which are destined for a common node can...

" telecommunications traffic, switching traffic from one circuit to another in the event of a network failure, supporting automated provisioning, and other applications. Having a DCS in a circuit-switched network provides important flexibility that can otherwise only be obtained at higher cost using manual "DSX" cross-connect patch panel

Patch panel

A patch panel or patch bay is a panel, typically rackmounted, that houses cable connections. One typically shorter patch cable will plug into the front side, whereas the back holds the connection of a much longer and more permanent cable...

s.

It is important to realize that while DCS devices "switch" traffic, they are not packet switches

Packet switching

Packet switching is a digital networking communications method that groups all transmitted data – regardless of content, type, or structure – into suitably sized blocks, called packets. Packet switching features delivery of variable-bit-rate data streams over a shared network...

—they switch circuits, not packets, and the circuit arrangements they are used to manage tend to persist over very long time spans, typically months or longer, as compared to packet switches, which can route every packet differently, and operate on micro- or millisecond time spans.

DCS units are also sometimes colloquially

Genericized trademark

A genericized trademark is a trademark or brand name that has become the colloquial or generic description for, or synonymous with, a general class of product or service, rather than as an indicator of source or affiliation as intended by the trademark's holder...

 called "DACS" units, after a proprietary brand name of DCS units created and sold by AT&T's Western Electric division

Western Electric

Western Electric Company was an American electrical engineering company, the manufacturing arm of AT&T from 1881 to 1995. It was the scene of a number of technological innovations and also some seminal developments in industrial management...

, now Alcatel-Lucent

Alcatel-Lucent

Alcatel-Lucent is a global telecommunications corporation, headquartered in the 7th arrondissement of Paris, France. It provides telecommunications solutions to service providers, enterprises, and governments around the world, enabling these customers to deliver voice, data, and video services...

. Not to be mistaken for Digital Access Carrier System

Digital Access Carrier System

Digital Access Carrier System is the name used by British Telecom in the United Kingdom for a 0+2 Pair gain system.- Usage :...

, a British pair gain

Pair gain

In telephony, pair gain is a method of transmitting multiple POTS signals over the twisted pairs traditionally used for a single traditional subscriber line in telephone systems. Pair gain has the effect of creating additional subscriber lines...

 system also using the acronym DACS'.

Modern digital access and cross-connect systems are not limited to the T-carrier system, and may accommodate high data rates such as those of SONET

Sonet

Sonet may refer to:* Sonet Records, European record label* Synchronous optical networking * Saab Sonett...

.