Selectrix is a digital model train control system developed by German company for model railway manufacturer Trix in the early 1980s. Selectrix is based on a data communication protocol developed originally by Siemens for communication between mainframe computers. Döhler & Haas offered their system to several model railway manufacturers in the 1980s. The only manufacturer interested in the system was Trix GmbH; this resulted in a licensing agreement between the two companies giving Trix exclusive marketing rights to the system. In 1999 the two companies mutually agreed to terminate their licensing agreement. Since then, Selectrix has become a widely recognized open standard and is supported by several equipment manufacturers in Europe. Selectrix is especially popular in smaller N scale and Z scale model railways. The MOROP has covered Selectrix data protocols partially in their NEM standards.