Which of the following is an example of automatic control?

Automatic control refers to systems that operate without human intervention, adjusting their operation based on feedback to maintain a desired state. In the context of amateur radio, one clear example of automatic control is repeater operation. Repeaters are designed to receive a radio signal and automatically retransmit it, facilitating communication over greater distances. They function continuously, adjusting to receive signals in real-time without requiring a human operator to manage the process.

While controlling a station over the internet can involve automation, it typically requires human input to initiate and manage the connection. Sending CW automatically using a computer or device may involve automation in transmission, but it is not an example of control in the same manner as the repeater, which operates independently to route signals. Similarly, automatic identification through computer technology can enhance operations, but it does not exemplify the broader concept of a system that operates autonomously like a repeater does. Thus, the operation of repeaters is a quintessential representation of automatic control in amateur radio systems.