The PRX205 (PRX/A) is a processor controlled reed relay telephone exchange developed by Philips Telecommunicatie Industrie BV (PTI) in Hilversum during the late 1960s and early 1970s.^[1] The first public switch was installed in Overvecht in Utrecht in 1972. About half of all sales were in the Netherlands; other countries with significant sales included Brazil, Indonesia, Peru and Jersey. The last PRX switch was taken out of service on 7 December 2010 at Volendam in the Netherlands.

The PRX digital version (PRX/D) was developed during the early 1980s in PTI's laboratories in Hilversum, Brussels and Malmesbury, Wiltshire but only went into limited production. PTI first went into partnership with AT&T in 1984 and then sold its remaining stake in the company to AT&T (later demerged into Lucent and subsequently merged to form Alcatel-Lucent) in 1987. After the takeover, the PRX/D development was stopped in favour of the AT&T 5ESS switch product, but development of PRX/A continued for some time afterwards. PRX/A systems were installed worldwide including many containerized versions and served reliably for 38 years.