Logical zones grouped by device function for D-303. Physical detection-zone boundaries (Clause 13) are defined on the as-designed drawing.
| Heat Detector | 9 |
| Beam Detector | 2 |
| Zone total | 11 |
| Manual Call Point | 4 |
| Zone total | 4 |
| Sounder | 8 |
| Zone total | 8 |
| I/O Interface | 3 |
| Zone total | 3 |