It was introduced in 1971 in Sweden, and lasted until 1987, when it was made obsolete by the NMT automatic service.
[citation needed] MTD was also implemented in Denmark and in Norway (from 1976), which allowed roaming within the Scandinavian countries.
In Sweden, the first mobile phone system was MTA (for Mobiltelefonisystem A), which was introduced in 1956, and lasted until 1967.
[citation needed] The second system, MTB (for Mobiltelefonisystem B), had transistorized mobile sets, was introduced in 1962, and lasted until 1983.
In 1976, the OLT system was extended to include UHF bands, incorporating MTD, and allowing international roaming within Sweden.