The simplest suppressors had MOVs and not much else. Packaging can sometimes help you to tell the difference by listing the internal components or providing a cutaway drawing of the innards. All the suppressors we tested come with lights to indicate if previous spikes have compromised the protection. But we found that those lights weren't always accurate. Better models are generously designed, leaving enough space between outlets so the transformer at the end of some accessory power cords won't cover adjacent outlets.
Most models also provide at least one telephone jack to shield the phone line from surges.
We didn't test that feature. All the surge suppressors we tested protected our computer under limited conditions. But households can experience numerous high-voltage surges, so your best choice is one of the top 14 models. They all withstood hundreds of surges ranging up to 6,000 volts. It was one of the best at suppressing the voltages in our tests and received a top design score from our experts.