External BTX: Decoder Module II for Commodore C 64 C personal computer

Commodore was very quick to offer a BTX module it developed jointly with Siemens. The plug-in module, which contains the decoder chip, is plugged into the port on the back of the computer and then connected to the post office's BTX connection box. The user can then make use of the benefits of BTX, such as BTX dialog exchange or saving pages.