A bi-directional amplifier (also known as a cell phone repeater or wireless cellular signal booster) is the most common way cell phone companies have been improving cellular coverage over the past few years. Nearly gone are the days when calls are dropped mid sentence. A bi-directional amplifier boosts cell phone signal by using an internal rebroadcast antennae in conjunction with a reception antenna and a signal amplifier. These aid the cellular broadcast towers that network providers base their signals from. These antennae are smaller and are used inside a building to improve cellular coverage inside when the walls might hinder a signal.
A bi-directional amplifier rebroadcasts cell signals received from outside of the building all throughout the building, in some cases even below the ground if necessary. Cellular coverage is important since most people have cell phones nowadays. The signal from main cellular towers sometimes is unable to get through thick concrete which can hurt cellular coverage. More advanced versions of bi-directional amplifier units allow more than one cell phone to use them at the same time, whereas the original models were only able to be used by one cell phone at a time. With a growth in the cell phone market, it only makes sense this kind of technology would continue to improve.