In embodiments, an emergency external defibrillator system is configured for use by a local rescuer in cooperation with a remote rescuer to assist a patient. The external defibrillator system includes a sensor to generate a patient value that represents a physiological parameter of the patient. The system also includes a communication module to transmit the patient value to another device of a remote rescuer, and to receive in response an incoming message that contains an encoded sound. For the local rescuer, the system also includes a screen to display the patient value, and a speaker to play the sound concurrently with the screen displaying the patient value. An advantage is that the local rescuer can receive guidance from the remote rescuer.