Which example best illustrates machine-to-machine (M2M) communication in IoT?

• A. Milking cow sensor indicates movement and a herd manager draughts her after milking
• B. An autonomous ambulance on an emergency call approaches an intersection and communicates with the signals to change the lights
• C. Sensors on a bridge detect strain and maintenance teams respond
• D. Smart thermostat adjusts heating automatically

Answer: (B)

Machine-to-machine communication is when devices exchange information and trigger actions without a human in the loop. The autonomous ambulance example fits this best because the ambulance and the traffic signals communicate directly with each other to adjust the lights in real time. This coordination lets the system prioritize the vehicle and navigate through intersections automatically, based on the data and rules built into the devices and infrastructure. That direct, automated interaction between two systems is the essence of M2M.

The other scenarios involve a human in the loop or a single device acting without another system to coordinate with, which doesn’t demonstrate M2M in the same clear way.