Mobile phone communications and wireless data and signals transmissions are required by various airport users. Airlines, telecommunications companies and other organisations need antennae to support their outdoor communication networks. To ensure aviation security and aesthetics at the airport, two towers in the north and south of the airport were built by Hong Kong CSL Ltd (CSL) to accommodate these antennae. The Northern and Southern Antenna Farms each occupying an area of 323 sq.m. cost HK$14 million to build. This cost is borne equally by all operators in the farms. CSL is licensed to operate the farms and has installed, for various organizations,65 antennae on the two farms.