The term DS3 is used to describe a digital telephone company circuit that carries multiple calls from one central office to another. These high-capacity circuits are called 'trunk lines' or sometimes 'tie trunks' or 'tie lines'. A DS3 carries the equivalent of 28 T1/DS1 circuits by decreasing the time slice alotted for each sample of data and multiplexes the T1's together to form the final DS3 data stream. The T1's are multiplexed together to form a single data channel on the DS3. The Digital Signalling protocol allows for the data on individual T1's or even DS0's to be extracted from the DS3 stream by any Digital Cross Connecting Switch containing a demultiplexor.
The phrase "level 3" indicates a level of multiplexing and should not be confused with the company of the same name.
This page is a place holder for a future tutorial.