Z21 is a modular system: ■ Begin with the Z21 start control centre and the Z21 multiMAUS. ■ Retrofit possible using the WLAN router and activation code, Art. no. 10814, thus allowing the use of a smartphone, tablet PC, Z21 WLANMAUS and computer (software-supported model railway control centre). ■ If you have your own WLAN router and are familiar with WLAN networks, then the activation code 10818 is all you need for the abovementioned retrofit.