http://cell-phone-booster-review.toptenreviews.com is a good source of information.
I used to use a Smooth Talker, and found that it added two bars to a weak signal, which meant that some "no signals" could be boosted to a usable two bars. (I don't know much about phones; my phone showed up to five bars for signal strength, and two bars were needed to have a decent connection.)
That was an analog phone. My Smooth Talker would not work with a digital phone. I never upgraded to a digital-compatible Smooth Talker, so my information may be somewhat dated.
