 The PRP was adapted from the British Army GL, "Gun Laying", radar system, and first went to sea in 1939 aboard several s, using the Type 280 radar.By 1941 the PRP was a common feature on the Type 280, 279 and 281 radars, and by late 1941 began to appear on the type 282P, 284P and 285P radar systems.The Type 282, 282M, 285, and 285M radars used a mechanical ranging panel that used a mechanical cursor placed over the ranging display, to estimate range and automatically transmitted the calculated range to either the HACS or FKC fire control computer.