Which system incorporates shared frequencies controlled by a computer that allocates frequencies per transmission?

The correct choice pertains to trunking systems, which are designed to efficiently manage communications for multiple users. In trunking systems, a centralized computer or control system allocates shared frequencies. This allows for dynamic use of channels, where the control system automatically assigns available frequencies to users as needed. This method minimizes waiting time and optimizes the utilization of radio spectrum, which is particularly beneficial in scenarios where many users might need to communicate simultaneously.

In contrast, simplex channels involve a single frequency used for one-way communication, and duplex channels allow for two-way communication on two distinct frequencies. Talk-around channels, typically used for direct communication when the main system is not available, do not rely on a centralized allocation of frequencies. Thus, trunking systems stand out for their advanced management of communication frequencies, ensuring efficient and scalable operations within emergency services and other organizations reliant on fast, reliable communication.