n in place for upwards of 100 years. Samuel Morse invented the telegraph in 1835. Alexander Graham Bell invented the telephone in 1876. In 1961, Bell Labs invented the T1 as a way to aggre- gate links between the central offices (COs) of the phone companies. It took almost 100 years to get from the first telephone to the invention of the T1. In contrast, consider the data world: the Arpanet was started in 1969, Robert Met- calfe and David Boggs built the first Ethernet in 1973, and Vint Cerf and Bob Kahn published the original TCP/IP standard in 1974. Hayes introduced the first modem in 1977 (300 bps, baby!), and 3Com shipped the first 10 Mbps Ethernet card in 1981. The first commercial router was sold in 1983. Let's think about that for a moment-the first commercial router was sold in 1983. Ask anyone around you if she can remember a time when there weren't phones. The telecom world is built on standards that work and have worked for a very long time. How often does your phone stop working? The telecom infrastructure is SO reliable that we expect reliable phone service even more than we expect reliable elec- trical service. (Cellular service is a whole different ball game, and does not apply to this discussion.) As with any technology, the engineers in the trenches (and their bosses behind the desks) like to sling the lingo. If you've spent your professional life around data equip- ment, telecom lingo might seem pretty foreign to you. To help bridge the gap between the data and telecom worlds, I've put together a list of terms that you might hear when dealing with telecom technologies. Most telecom words and phrases have standard meanings defined in Federal Standard 1037C, titled "Telecommunications: Glossary of Telecommunication Terms." These definitions are often very simple, and don't go into a lot of detail. The terms I'll cover here are the ones most often encountered in the life of a network administrator or engi- neer. If you need to know what circuit noise voltage measured with a psophometer that include