Logical zones grouped by device function for D-309. Physical detection-zone boundaries (Clause 13) are defined on the as-designed drawing.
| Optical Smoke | 17 |
| Heat Detector | 3 |
| Zone total | 20 |
| Manual Call Point | 3 |
| Zone total | 3 |
| Sounder + VAD | 5 |
| Zone total | 5 |
| I/O Interface | 2 |
| Zone total | 2 |