Central Office Building Picutures
Frequently Asked Questions


Here are some answers to some frequently asked questions regarding this site.

What is a Telephone Central Office?

A Telephone Central Office (sometimes known as a Telephone Exchange) is the central location point where telephone switching occurs for a particular region. A telephonically served region is technically known as a "wirecenter" and a location for billing purposes is called a "ratecenter". Often times they're one in the same, but in large ratecenters you may have many wirecenters. Each wirecenter has a telephone switch that handles calls for subscribers, and these telephone switches are housed in buildings known as Central Offices (or telephone exchanges).

Inside each Central Office is a telephone "switch" that handles calls between subscribers or from subscribers to other switches in the network. They can have links (or trunks) to telephone "tandems" where many calls are handled for long distance communications. This site mainly focuses on local switching system buildings in the United States and Canada.

What are the types of Telephone Central Office switches?

In the United States and Canada, the main types of central offices switching systems are the 5ESS series (Lucent/Western Electric), the DMS series (Nortel), the EWSD series (Siemens), GTD5-EAX (Automatic Electric), DCO series (Stromberg-Carlson) and others. As time has moved forward, these traditional circuit switched systems are being replaced with more modern packet switching systems from Metaswitch and Ribbon Communications. However they are mostly still housed in traditional central office buildings.

If you're looking for telephony technology in general (and more details on these telephone switching systems please see our sister site Telephone World (a sister site to this one).

What is the goal of the site?

The goal of the site is to collect pictures of all of these Telephone Central Office (aka telephone exchange) buildings before they completely disappear. As landline calls are dwindling in number, the fate of these buildings are in question. So far they're mostly still in existence, but over time we expect them to be consolidated and some even disappear completely.

Most of these buildings are not ornate and are built to serve a purpose. But many older ones were built in the "grand" days of telephony and due to the size of the switching systems of yesteryear (step by step and crossbar) some of them are quite large. More recent buildings are small and utilitarian. We strive to capture pictures of all of them.

How many Central Office buildings are there?

As of January 2021 there are around 18,800 central office buildings in the United States and around 3,100 in Canada. As of October 2021, we list over 6,200 of these central offices, or only around 1/3 of all of them.

This is not the only site that has pictures of Telephone Central Offices. Please see The Central Office, operated by a former telephone company employee.

Site Inspiration and Dedication

This site is dedicated to two people (who are no longer with us) who were the inspiration for the site. Mark Cuccia was a telephone historian who helped out with a number of the historical aspects of this site and of Telephone World (a sister site to this one). Parris Wood ran a similar site called Telebeans that collected pictures and information of telephone central offices in the Mid-Atlantic region. (I've preserved his website called Telebeans for posterity.)

If you're looking for sounds of what the telephone network USED to sound like in the 1970s, please visit Evan Doorbell's Telephone Tapes (another sister site to this one).

Can I Contribute?

We are ALWAYS looking for volunteers to take pictures of telephone central offices. If you wish to get involved, please let us know and we can help you with locating them. And please remember that this site's goal is for historical preservation and not to cause any harm.

And if you have questions please drop us a line and we'll try to answer them.


Copyright 2021 Telephone Central Office Building Pictures
Page last modified October 17, 2021
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