A gold box is an illicit telecommunications device built to bridge two telephone lines, automatically answering an incoming call on one line and dialing out on the second line to connect the two parties. Phone phreaks used it to obscure their physical location or to steal long-distance service by routing calls through a compromised corporate PBX.
Heard on the job
The investigators found a gold box wired into the punchdown block, bouncing calls out to an international number.