Which devices are always placed between L1 and the output devices?

• A. The power supply
• B. The output devices
• C. The input devices
• D. The wiring harness

Answer: (C)

The essential idea is that input devices serve as the control path between the live supply (L1) and the loads (the output devices). In a basic control circuit, L1 feeds the system, and the inputs act as switches or sensors that must be closed to complete the circuit toward the outputs. When an input is activated, current can flow from L1 through that input and on to energize the rest of the control path, ultimately powering the output devices. If the input is not active, the circuit is open and the outputs stay off. This arrangement makes input devices the components that determine whether the outputs receive power.

The other elements don’t sit in that control path in the same way: the power supply is the energy source for the whole circuit, not a device placed between L1 and the outputs, the output devices are the loads that consume the power, and the wiring harness is just the physical cables connecting everything.