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Central Office Tour: Where Does That Wire Go?

Photos by David Ogburn

Washington Apple Pi Journal, reprint information

When you fire up your modem and "dial in" to the Internet, what happens after the phone line disappears into the panel in your wall? If you are one of the fortunate who can get DSL service, you might know that DSL requires you to be within a certain number of feet of a "CO," or "central office," but what does that mean? Does a "central office" look like a YMCA gym, or the local Department of Motor Vehicles, or the bridge of the Star Ship Enterprise?

Washington Apple Pi member David Ogburn took these digital photos of the inside of a Verizon central office. While the details may differ somewhat, most telephone central offices throughout North America look much the same. To see a larger version of any photo, click on the photo.

These are the cables carrying the copper wires from your home into the cable vault below the central office and up to the distribution frame.

The wires are separated into the copper pairs that provide your telephone service and run into the back of the distribution frame.

This is the front of the distribution frame where the copper pairs are connected one-by-one to the Central Office switch. If you are patient, you might try this, an even larger, higher resolution version of this photo.

This shows an entire row of the distribution frame.


This is one row of the central office switch, a Lucent 5E. Each cabinet holds a number of cards, each containing a Motorola processor.

 This bay contains the multiplexers for Litespan equipment. Litespan permits your phone service to be provided over fiber optic cable to equipment cabinets near your neighborhood that contain matching multiplexers and a crossconnect box to connect your service to the copper pair that serves your house.

This is multiplexing equipment that provides high-speed data service over fiber optic cable.

This is the multiplexing equipment for an OC 192 circuit that can carry 9.6 GB of data per second. This equipment costs approximately $250,000.

This is a fiber cross connect point where the data from the multiplexers leaves the central office on fiber trunks.

This is bank of DSL multiplexers. Each box (there are three in each of these racks) provides 48 DSL circuits. DSL must be provided end-to-end over a copper pair.

Local exchange carriers like Verizon are required to provide collocation space to permit CLECs (competitive local exchange carrier) to locate equipment in the central office. This is a row of collocated CLEC equipment.

CLECs preferring more security for their equipment can lease caged collocation space in the central office.