The Castle Radio-Zone expander will accept signals from 7 or 29 Class VI wireless detectors or repeaters, depending on its mode of operation. Each detector may be fully supervised, and there is provision for low battery warning. Assigning wireless detectors to individual zones is simplicity itself, and signal strength is displayed for each detector.

The Radio ZEM is compatible with any Euro-MERiDIAN panel that can be expanded with ZEMs and will provide 7 wireless zones where the panel is in End of Line mode, or 29 wireless zones where the panel is in iD mode.