
Ei Electronics Ei650W-3XD Smoke detector

Ei Electronics Ei650W-3XD Smoke detector
I am unclear what I need to be able to network Ei650 smoke alarms. On the one hand, there is an "Ei650W smoke alarm" and an "Ei650 radio smoke alarm". In the instructions for a detector I have already bought, it also says that the Ei650W model (and others) can also be networked by radio, but this requires the Ei650M radio module. Do I understand correctly that 1. this radio module must be purchased separately for the Ei650W and 2. it is already included in the above-mentioned "Ei650 radio smoke alarm"? Are there any other differences between the Ei650W and the Ei650?