Which device is typically used for collecting audio signals in communication systems?

The device that is typically used for collecting audio signals in communication systems is the microphone. A microphone functions by converting sound waves, which are variations in air pressure, into electrical signals. This process enables the capture of vocal sounds or other audio inputs, making it essential for communication applications such as telephony, broadcasting, and recording.

Microphones come in various types, including dynamic, condenser, and ribbon, each tailored for different audio capturing scenarios. The functionality of microphones makes them invaluable in environments where sound needs to be transmitted over distances, recorded, or processed for various audio applications.

In contrast, other devices play different roles: an antenna is primarily used for transmitting or receiving radio waves, a speaker is designed to convert electrical audio signals into sound waves for playback, and a transmitter serves to send information, which can include audio signals, but does not collect or capture those signals. Thus, the microphone is specifically designed for the collection of audio, making it the correct choice in this context.