The DBS-1 Detector Base sounder can be used alongside the PSD-2 / FHD-2 and RHD-2 detectors.
This base will not only detect smoke or heat (depending on what detector you have in place) but it will also trigger the alarm sounder.
The DBS-1 features are:
Sound output @ 1m - 93 decibels
Current: 18mA