For example, the article referred to ADS-B ground stations as ADS-R stations, but they are not. The general term is Ground Based Transceiver (GBT). ADS-R is only one function of the GBT in which the GBT receives an ADS-B transmission on one data link frequency (978 or 1090 MHz) and rebroadcasts that transmission on the other frequency. This rebroadcast function only occurs if a client aircraft (ADS-B Out and In equipped) indicates in its transmission that it can receive only one frequency, and if the target aircraft is broadcasting ADS-B Out on the other frequency. Plus, both aircraft must be within a defined proximity (generally 15 NM horizontally and 3500 feet vertically) of each other.