Analog output signals from a PLC typically require which component?

Analog output signals from a Programmable Logic Controller (PLC) typically require a special interface card because PLCs primarily handle digital signals. The interface card serves the crucial role of converting the digital signals generated by the PLC into analog signals that can be used to control various devices, such as valves, actuators, or other equipment that operate on analog control principles.

The special interface card allows for precise manipulation of a range of analog output values, ensuring that the output accurately reflects the system requirements. It is designed to manage the nuances of analog signal processing, such as handling voltage or current levels and ensuring compatibility with the devices being controlled.

In contrast, the other options listed do not provide the necessary functionality for managing analog outputs. A relay typically works with digital signals to switch devices on and off. An indicator light is used for signaling and visual feedback, not for processing or converting signals. A parallel port is a type of connection interface that does not inherently provide the conversion capabilities required for analog signals. Thus, the special interface card is essential for effective analog output management.