Between them, these two companies operate the broadcast infrastructure for UK terrestrial TV and most radio broadcasting, both analog and digital.
BT also operates a number of telecommunications towers in the UK. At one time these were intended to be used as the backbone for a national line-of-sight digital microwave telecommunications network. One of the most famous of these is the BT Tower in London. However, the introduction of fibre optic network technology rendred these microwave towers largely obsolete.
Below the level of the major telecommunications towers, cellphone operators run roughly 23,000 base stations. In urban areas, these are almost all rooftop sites or microcells, but in rural area these are often on masts, frequently owned by one of BT, NTL or Crown Castle.
There are also numerous military communications sites in the UK, operated by various wings of the armed forces.
To do: private point-to-point microwave links, CCTV, wireless Internet access