In radio systems, what is a multiplexer used for?

A multiplexer is a critical component in radio communication systems, serving the primary function of combining multiple signals into a single signal for transmission. This process allows multiple data streams to share the same communication channel, efficiently using the available bandwidth. By doing so, the multiplexer enables simultaneous transmission of different channels without interference, optimizing the use of the transmission medium.

The function of a multiplexer is especially vital in modern communication systems where bandwidth is a limited resource. It directly impacts the efficiency and capacity of data transmission, ensuring that multiple signals can be sent over a single line without degradation of the individual signal quality.

Other choices present functions that do not align with what a multiplexer is designed to achieve. For instance, increasing signal strength is typically handled by amplifiers, while filtering unwanted frequencies is managed by filters. Adding noise to a signal does not have a practical application in efficient communications and would undermine the purpose of achieving clear and reliable transmission. Thus, the role of the multiplexer is specifically attributed to the combination of signals for effective communication.