What device combines multiple video channel inputs into one signal for recording purposes?

The correct answer is a multiplexer. A multiplexer serves a crucial role in video surveillance systems by combining multiple video channel inputs into a single output signal. This process allows for efficient management and recording of footage from various sources, such as different cameras watching different areas.

By consolidating these channels, a multiplexer enables a more streamlined recording and monitoring process, allowing security personnel to focus on numerous feeds without being overwhelmed by multiple separate recordings. Additionally, this is particularly important in loss prevention settings, where multiple areas need to be monitored simultaneously for potential theft or other security concerns.

In contrast, the other devices listed serve different purposes. A video synthesizer is primarily used to create new video signals from existing ones, often utilized in creative fields rather than straightforward surveillance. A signal amplifier enhances the strength of video signals, ensuring they can be transmitted over long distances without degradation, but it does not combine inputs. A video mixer is designed to blend various video inputs for live production or broadcasting rather than for recording purposes. Each of these tools has its specific use in video technology, but the multiplexer is uniquely suited for the stated function of integrating multiple video channels into a single signal for recording.