z21® is a modular design digital system: ■ Begin with z21®start and MULTIMAUS®. ■ Upgrading with a WiFi router and activation code, Art. no. 10814 and thus use of smartphone, Tablet-PC, WiFi MULTIMAUS® 10813 and computer (Software-protected model train control) is possible. ■ If you already have your own WiFi router and you know how to work with WiFi networks, then the activation code 10818 is sufficient for the aforementioned upgrading.