Telecom For Dummies

Before you can have a conversation about dedicated service, you have to understand the language. When you have the lingo down, the rest all falls into place. Here’s the lowdown on the basic terminology:

• Local loop: The copper wire or fiberoptic cable that spans from your carrier to your office. Your carrier charges you a rental fee for the local loop every month and a one-time fee when it’s installed.

• Central Office or CO: The building where your local carrier houses a large piece of hardware called a Class 5 (local services) switch, which routes calls, provides dial tone, and all the other telecom services you know and love. Also in this building are several tons of batteries to sustain the Class 5 switch in the case of a large-scale power outage.

• Point of Presence or POP: The building where your long-distance carrier houses a large piece of hardware called a Class 4 (long-distance) switch, which routes calls and provides all the long-distance services you know and love.

• T-1 or DS-1: A dedicated circuit that can be broken down into 24 individual channels, each of which can support a call. The T-1 circuit is also called a DS-1, and is the basis of all dedicated circuits; all voice circuits are broken down to T-1 level.

• DS-3: A dedicated circuit that holds 28 T-1s. This is a big cable. In fact, it doesn’t even resemble a standard phone line that you plug into your phone; it looks more like the big, fat, round cable that connects into your television.

• OC-3: A dedicated circuit that holds three DS-3s. This is an even bigger big cable. It’s a fiberoptic circuit and requires an optical multiplexer (or optical MUX) to receive it. An optical multiplexer is a device that puts the electrical DS-3 circuits into a fiberoptic cable. Optical multiplexers use light rather than electricity for signaling.

• DS-0: The atomic unit of telecommunications. A DS-0 represents the single channel necessary to carry one phone conversation. You need 24 DS-0 circuits to make up a T-1 or DS-1. That makes DS-0 the primary unit of measure for dedicated circuits in the United States.

•  Technical Stuff  E-1: Outside the U.S., the basic unit for dedicated services. E-1 circuits carry 32 DS-0 circuits, 30 call channels, plus one channel for timing and one channel for signaling. The European standard was developed after the American DS-1 standard was set up.