Bosch F220-B6 12/24 VDC Two-wire Base - For Smoke Detector - Surface Mount - 12 V DC, 24 V DC - Plastic - Off White
The F220-B6 Detector Bases work with the F220Photoelectric Smoke and Heat Detectors. The F220-B6is a 12 V or 24 V base for two-wire loops. The otherbases in this family are 12 V or 24 V bases for four-wireloops.