What you want to ask is what caused the serious voltage drop of Qingdao fire bus? The reason for this is the following：

1, the line is grounded, and the resistance of the conductor to the ground is low.

2. Wiring error, for example, the second signal bus is connected to the 24V terminal of the module.

3. The wire is too long or the wire material is poor. Generally, the line resistance of electric wires does not exceed 50 ohms.

4, equipment damage, when the circuit board of the equipment circuit board is broken down or damaged, it will also cause voltage drop.