Enlarge / A Surfboard modem. (credit: Arris)

Last year, Charter was punished by the Federal Communications Commission because it had spent two years preventing customers from using their own modems. As a result, the nation’s second-biggest cable company must now follow a shortened testing procedure to verify third-party modems and file compliance reports every six months detailing its efforts to let customers attach their own modems to its network. The company also had to pay a $640,000 fine.

The FCC’s rules are clear: cable companies must let customers use their own equipment (including modems) unless it isn’t compatible with the network or unless it would cause some kind of harm or was designed to let customers obtain services they didn’t pay for. But if you’re a customer of a company that simply refuses to let you use a third-party modem, getting what you want is not easy.

Elbert Davis of Crown City, Ohio, is a customer of Armstrong, a much smaller cable company with about 800,000 subscribers. He owns a Motorola/Arris Surfboard SB 6121 modem that he’d like to use instead of the Arris CM820 supplied by Armstrong. But the cable company won’t allow it, despite offering no proof that it would harm the network or is incompatible. (The Surfboard is a DOCSIS 3.0 device certified by CableLabs, the cable industry’s equipment testing body.)