Optional expansion module based on EnOcean for expanding AGFEO system telephones of the type ST 42 (IP) and ST 45 (IP) into a SmartHome central unit on ES and HyperVoice systems. The transmitting and receiving module based on radio technology integrates EnOcean components into SmartHome solutions of the respective communication systems. Max. 10 pieces can be used per system. The En module 42 requires the current system firmware version at the time of delivery.