A One Star designation indicates that the device has undergone DOCSIS testing by Comcast and has received the relevant Underwriters Laboratory ("UL"), Federal Communications Commission (FCC), and CableLabs certifications. Comcast's DOCSIS certification supplements CableLabs testing by adding things like performance and interoperability tests. This helps to ensure that, for example, a given device can support a given service tier's speed.
A Two Star designation indicates that the device has undergone all of the One Star tests as well as a basic Physical and Environmental (P&E) evaluation. Such basic P&E testing indicates basic manufacturer self-certification of a subset of P&E tests.That basic P&E evaluation is intended to address a number of important performance and safety issues, which tests from UL, the FCC, and CableLabs do not address. Some of the things P&E tests check for include areas such as device performance and safety during overheating, power interruptions (including power outs), radio frequency (RF) interference, electrostatic discharge, electrical surges, and network impairments.
A Three Star designation indicates that the device has undergone all of the Two Star and One Star tests as well as a full Physical and Environmental (P&E) evaluation. Such full &E testing indicates that all P&E tests were performed and that these tests were overseen in person. This is the highest and most thorough level of testing available.