A telco can is an outdoor enclosure

Enclosure (electrical)

An electrical enclosure is a cabinet for electrical or electronic equipment to mount switches, knobs and displays and to prevent electrical shock to equipment users and protect the contents from the environment...

 or metal box where telephone local loop

Local loop

In telephony, the local loop is the physical link or circuit that connects from the demarcation point of the customer premises to the edge of the carrier or telecommunications service provider's network...

 wires come together to be spliced into a larger cable that then runs to the Central Office. They are often just brown metal boxes (dark green in the UK) on the street or side walk. Telco cans are often the victim of graffiti

Graffiti

Graffiti is the name for images or lettering scratched, scrawled, painted or marked in any manner on property....

 and used for advertising posters, as they provide a surface on which to put posters, and are not often maintained.

Internal equipment

Inside the telco can, a lineman can also access each local loop for testing purposes; they are typically arranged in busses of 100. Here a lineman can clip a lineman's handset

Lineman's handset

A lineman's handset is a special type of telephone used by technicians for installing and testing local loop telephone lines. It is also called a test set, butt set, or buttinski.-Components:...

 onto the wire and perform various tests such as noise on line, ring back, dial out, and access the DATU

Datu

Datu is the title for tribal chiefs, sovereign princes, and monarchs in the Visayas and Mindanao Regions of the Philippines. Together with Lakan , Apo in Central and Northern Luzon, Sultan and Rajah, they are titles used for native royalty, and are still currently used in the Philippines...

 and other test circuits. Having many local loops available, they can be used by a Phreaker for beige box

Beige box (phreaking)

In phone phreaking, a beige box is a device that is technically equivalent to a telephone company lineman's handset — a telephone fitted with alligator clips to attach it to a line.-Construction:...

ing.