What does it indicate when the LED next to a relay in a microprocessor-controlled system is illuminated?

When the LED next to a relay in a microprocessor-controlled system is illuminated, it generally indicates that the microprocessor is actively controlling the relay coil by providing a ground. In this context, the relay coil requires a complete circuit to energize, which is typically achieved when the microprocessor sends a ground signal.

This setup allows the system to control various components based on the processing of signals and inputs it receives, enabling features such as temperature regulation or operational status of the cooling unit. The illumination of the LED serves as a visual confirmation that the relay coil has received the necessary signal from the microprocessor to engage.

While other options might suggest alternative interpretations for an illuminated LED, the specific scenario of the microprocessor supplying a ground signal aligns most accurately with the functioning of relays in microprocessor-controlled systems.