What equipment confirms that a transmitted signal is received?

The portable radio is crucial for confirming that a transmitted signal has been received because it is specifically designed to both transmit and receive radio signals. When a signal is sent from a transmitter, the portable radio can decode and play the received signal, allowing the user to verify that the communication was successful.

Handheld microphones are primarily used for capturing audio to be transmitted but do not have the capability to receive signals. A signal generator produces signals for testing and is not involved in receiving communications. A speaker system outputs audio but, in isolation, does not confirm whether a signal has been received, as it does not have the receiving functions that a radio does. Therefore, the portable radio stands out as the correct answer, as it fulfills the requirement of confirming the reception of a transmitted signal effectively.