An air hammer includes an air hammering mechanism and a vibration suppressing device to absorb the vibration transmitted from the air hammering mechanism. A wafer including a plurality of semiconductor chips is provided. Each ultrasonic base station is configured to receive the timing synchronization information and to transmit a corresponding ultrasonic location code in a time period based on the received timing synchronization information. The indication can be direct, by visual inspection of the displaced head, or indirect by the displacement of the head activating a transmitter.