In the study of fire alarm systems, we encounter the concepts of “bus control panel” and “multi-line control panel”. So what is bus control? What is multi-line control? What fire protection equipment do they control? Let’s take a detailed look.
The so-called fire alarm system multi-line control means that each detector (device) has an independent signal loop with the controller, and the detectors (devices) are independent of each other, with all detection signals input to the controller in parallel. In simple terms, it is a point-to-point connection.
On the other hand, the fire alarm system bus control refers to a bus loop formed by two or four wires, where all detectors (devices) are connected in parallel on the bus, and each detector (device) has its own independent address code. The controller generally uses serial communication to query each detector (device) by different addresses.
Currently, in China, detectors and other devices such as manual alarms, fire hydrant buttons, sound and light alarms, modules, etc., all adopt the bus control system. Bus control uses fewer wires and is convenient for design and construction, thus it has been widely used. The commonly referred to two-wire bus is clearly bus control, referring to two signal wires. The four-wire bus adds two power wires to the signal wires.
Compared to multi-line control, multi-line control uses more wires and has higher costs, and the wiring can be cumbersome. However, multi-line control has not completely exited the stage, as key fire protection equipment such as pumps and fans still require multi-line control. This is because the stability of multi-line control is higher than that of bus control; since they are independent, they are not affected by other devices or line faults. Although multi-line control uses more wires, the circuits are simpler and more stable, and will not cause partial paralysis or even system failure due to a fault at a single point.
Both types of wiring have their pros and cons. After development, our country is currently in a situation where detectors (devices) use bus connections, while linked equipment such as pumps and fans use multi-line connections. Multi-line fire alarm controllers are becoming hard to find, while abroad, there are still multi-line fire alarm controllers for detection equipment. The use of multi-line controlled fire alarm systems is relatively rare in China’s fire protection industry, although gas detection alarm systems using multi-line control are still quite common.
