The KX series of telephone boxes in the United Kingdom was introduced by BT (British Telecom) in 1985. Following the privatisation of BT in 1984, the company decided to create a newly designed and improved take on the British telephone box, which at this point consisted of only red telephone boxes which BT had recently acquired, the most common being the iconic K6 box. These red boxes were considered flawed in parts by BT for several reasons, including cost, lack of ventilation, accessibility and maintenance. BT announced the £160 million series of new boxes, the KX series designed by GKN, as well as announcing the eventual replacement of all existing telephone boxes. The main telephone box in the KX range is the KX100. Upon launch, there were five models in total. The boxes were produced at a rate of 5,000 a year, with the total count of all BT-owned kiosks reaching 137,000 by 1999, a number which has since decreased by more than seventy per cent.
Whilst the updated functions of the KX series were praised, the designs were widely criticised and were seen as inferior to the red telephone boxes. The plan to replace the red boxes was also criticised. Many of the models in the KX series were revamped graphically after BT changed their logo in 1991, and production of the KX100 stopped in 1996 with its replacement, the KX+, attempting to address the criticisms that the original KX100 had received by revising its design to incorporate elements of older red telephone boxes. Later versions of the KX+ incorporated broadband connection. BT was reported to have stopped making telephone boxes altogether in 2001, although this was later denied with the introduction of the ST6 in 2007, which saw the end of the KX series.