The mine hunting vehicle (MHV) is equipped with active sonar comprising a transmitter and a receiver. This means that the range at which it can detect a target depends on the reflecting area of the target, the power of the transmitter, the gain of the transmitting and receiving array and the sensitivity of the receiver. The transmitted energy is propagated according to an inverse square law; so a target at a range of 1,000m will receive only a quarter of the power of a target at 500m. The reflected signal from the target is also propagated according to an inverse square law, so that the signal received by the MHV follows an inverse fourth power law. For example a target at 1,000m will deliver to the receiver only one sixteenth of the power from a target at 500m.

CHECKMATE is equipped with passive sonar comprising a sonar receiving array and a receiver. The signals it receives from the MHV are following an inverse square law so if the gain of the array and the sensitivity of the receiver are similar to that of the MHV it will detect the presence of the MHV well before the MHV has any chance of detecting CHECKMATE. In the diagram above CHECKMATE detect the MHV at 2,000m whilst the MHV may only detect CHECKMATE at 1,000m.

In addition, CHECKMATE is largely buried in the seabed, so that it's reflecting area is much less than that of a tethered conventional mine.