British Telecom microwave network

From the late 1950s to the 1980s it provided a large part of BT's trunk communications capacity, and carried telephone, television and radar signals and digital data, both civil and military.

Its use of line-of-sight microwave transmission was particularly important during the Cold War for its resilience against nuclear attack.

It was rendered obsolete, at least for normal civilian purposes, by the installation of a national optical fibre communication network with considerably higher reliability and vastly greater capacity.

[1] In 1939 the Post Office placed a contract with EMI for an experiment in the relaying of television signals to Birmingham.

Each relay station consisted essentially of back-to-back rhombic antennas on opposite sides of a hilltop, connected via an amplifier.

The stations were at:[6] The term 'backbone' is often applied to the core of a communications network, i.e. the part that provides high-capacity links over long distances between major nodes.

In the early 1950s, the term was used by the General Post Office (BT's predecessor) to describe a chain of microwave links designed to provide resilient communications in the event of nuclear war.