Telephone exchange chaining in the - a form of phone phreaking
This BT-owned telephone exchange is notable as it contained one of the last working Strowger (electro-mechanical) exchanges to be taken out of service in Scotland. Description from geograph.org.uk. I searched for this on bing.com/images
German prisoners, captured by the Polish Home Army during the Warsaw Uprising of August to October at the city's central telephone exchange. Original Publication: Picture Post - 9259 - Pictures From The Grave - - pin by Paolo Marzioli
A telephone exchange is a telecommunications system used in the public switched telephone network or in large enterprises. Shown is a 1924 PBX telephone switchboard on display at the Atlanta History Center in Atlanta, Georgia.