Summary: I work in a metal building and have no signal at all with my AT&T cellphone. I had been using an external antenna but was limited to where I could use my phone by the length of the cord. After purchasing the unit, it took all of 15 minutes to install and worked perfect when I powered the unit up. Phone clarity is perfect, I went from zero bars to a full five bars signal strength. I intend to buy another for my home.