A telco can is an outdoor enclosure or metal box where telephone local loop 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 and used for advertising posters, as they provide a surface on which to put posters, and are not often maintained.
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 onto the wire and perform various tests such as noise on line, ring back, dial out, and access the DATU and other test circuits. Having many local loops available, they can be used by a Phreaker for beige box.