- 2 wires with EOL
- Old fashion design
- Break in line will affecting the full detection

Analogue Addressable
- Loop configuration
- Smoke density data transmit back to Control Unit
- Requires special type of cable due to massive data flow

Digital Addressable
- Loop configuration
- Only alarm/fault signal will transmit back to control unit
- Less requirement on the cable

Free Topology
- Combination of loop and stub lines
- Easy to expand
- Prefect for upgrading
- Transmission through radio waves
- Real time monitoring for alarm and fault