Question about Abus Smartvest wireless smoke and heat alarms

Unlike other radio smoke detectors, the manual seems to say that one of the detectors must be configured as the central detector. Does this mean that all other detectors must be able to connect directly to the central detector, or can this also be done via another detector? So if a detector is too far away from the device defined as the central detector, an intermediate detector automatically acts as a repeater, so to speak, by forwarding the alarm to the central detector, which in turn forwards it to all the others, possibly also via another detector? If this is indeed the case, I wonder why one of the detectors has to act as a central unit at all. Otherwise, the only affordable alternative I can see is the HomeMatic smoke detector, where all the detectors simply communicate with each other. But this device has a non-replaceable battery, which I find less great, even though they are supposed to last 10 years. I'm simply looking for an inexpensive (< CHF 100 per device) radio smoke detector (but don't want to be dependent on WLAN or Bluetooth) where you can install three to five devices somewhere and they all just have to reach each other together somehow, and the device should have a replaceable battery. Of course, there should be an acoustic alarm. Smarthome integration is not necessary.