Ans. is 'a' i.e., Zoll automatic external defibrillator Monitor for chest compressions in cardio pulmonary resuscitation A novel monitor for the chest compressions is a device incorporated into the chest compression pad of the ZOLL AED - PLUS automatic external defeibrillator. The sternal compression pad located between the stick on defibrillating electrodes includes an accelerometer. The signal from this device is doubly integrated to produce a measure of compression depth monitored by the device. Auditory feedback can be provided to the rescuer if chest compression depth so monitored falls outside the recommended range. Such technical aids improve the efficacy of external chest compressions and thus the rescue of patients.