Cell Phone Repeater, GSM Repeater
GSM Repeaters are amplifiers for mobile radio systems at various frequency bands (900, 1800, 2100 MHz, GSM and/or UMTS/3G). They are used at locations where the indoor reception of GSM/3G signals is impossible or insufficient. This is the case with many modern (or renovated) buildings which are perfectly shielded for better energy efficiency, but also against radio waves. Other scenarios are underground buildings like parking garages, cellars, storage rooms etc.