A phreaking device built by modifying a standard telephone keypad to include a fourth column of buttons. This creates a four-by-four grid that generates the specialized dual-tone multi-frequency signals known as A, B, C and D. Telephone technicians traditionally used these extra tones for internal network routing and priority access controls.
I hooked up a silver box to the test set to see if the switch would still accept the priority tones.
The extra tones generated by a silver box were originally reserved for the military Autovon network to signal different levels of call priority.
Related terms
Blue box
A historic electronic toll-fraud device used to manipulate long-distance telephone switches.
Beige box
A modified telephone equipped with alligator clips for tapping directly into telephone lines.
Gold box
A historic phreaking device that acts as a line diverter to route incoming calls to a different number.