The fuzes used on mortar rounds are designed to activate the fired round at the desired time or place (fig. 14-11). There are three types of fuzes used with the 60-mm mortar ammunition: impact, graduated time, and variable time.

The IMPACT FUZE causes the round to function when it comes in contact with an object. Impact fuzes can be either point detonating (PD) or base detonating. Point-detonating fuzes that function immediately upon impact are called superquick (SQ). Point-detonating fuzes that have some penetration into the ground before functioning are called quick (Q). Point-detonating fuzes that enter the ground before functioning are known as delay (D).

The GRADUATED TIME FUZES cause the round to function at a prescribed (set) time after the round is fired. Graduated time fuzes may function at the prescribed time only. These fuzes are known as time (T) fuzes. Graduated time fuzes may also have an impact element that causes the fuze to function on impact if it does not function at the set time. These fuzes are known as TIME AND SUPERQUICK (TSQ) FUZES.

The VARIABLE TIME FUZES have their own radio transmitter and receiver. They transmit a radio signal. This signal is reflected back to the fuze. As the fuze (round) approaches an object, the strength of the

Figure 14-11.-Fuzes.

reflected signal increases. When the returning signal reaches a predetermined strength, the fuze explodes the round. These fuzes are known as proximity or VARIABLE TIME (VT) FUZES. The object that reflects the signal is not necessarily the target. It maybe any object that can reflect the signal. The VT fuze explodes at a height of about 1 to 6 meters over normal terrain; however, the better reflecting surfaces cause the fuze to explode at a higher height and the poorer reflecting surfaces at a lower height. Trees increase the height of burst. Even clouds have caused the fuze to detonate.