S3 has more bandwidth than a T1, what she's really saying is that the DS3 will deliver higher throughput, in that it is capable of 45 million bits per second (Mbps), as opposed to the T1's paltry (by comparison) 1.54 Mbps. In common usage, the terms bandwidth and throughput are interchange- able. A more accurate term when referring to links might be data rate, as a DS3 can deliver the same number of bits in a shorter amount of time than a T1. BERT stands for Bit Error Rate Test. You'll often hear the term "BERT test," although this is technically redundant because the T in BERT stands for test. Still, saying, "We're going to run some BERTs on the T1" will make everyone look at you funny. BERT tests are disruptive tests run on a link to validate the data integrity of the circuit. A BERT test is usually run by putting the remote end of the link in loop- back and sending out a pattern of ones and zeros. How the data is returned from the far-end loopback can help determine whether certain types of problems exist Chapter 19: Telecom Nomenclature in the line. Some of the common types of BERT tests you may hear mentioned include QRSS (Quasi-Random Signal Source), 3 in 24, 1:7 or 1 in 8, Min/Max, All Ones, and All Zeros. Each of these patterns stresses a link in a certain pre- dictable way. A device used to perform BERT testing on a T1 is called a T-Berd. Central Office (CO) The central office is where phone lines from residences or businesses physically terminate. COs have the necessary switching equipment to route calls locally, or to another carrier, as needed. When you make a call that is destined for some- where other than your premises, the CO is the first stop. With technology like T1, the copper connection from your location will proba- bly terminate at a CO, where it may be aggregated into part of a larger SONET system. Channel bank A channel bank is a device that separates a T1 into 24 individual analog phone lines, and vice versa. Today, PBXs usually take care of partitioning T1s into analog lines, thereby eli