The early wartime Royal Navy procedure was to sweep the ASDIC in an arc from one side of the escort's course to the other, stopping the transducer every few degrees to send out a signal. Several ships searching together would be used in a line, apart. If an echo was detected, and if the operator identified it as a submarine, the escort would be pointed towards the target and would close at a moderate speed; the submarine's range and bearing would be plotted over time to determine course and speed as the attacker closed to within . Once it was decided to attack, the escort would increase speed, using the target's course and speed data to adjust her own course. The intention was to pass over the submarine, rolling depth charges from chutes at the stern at even intervals, while throwers fired further charges some to either side. The intention was to lay a 'pattern' like an elongated diamond, hopefully with the submarine somewhere inside it. To effectively disable a submarine, a depth charge had to explode within about . Since early ASDIC equipment was poor at determining depth, it was usual to vary the depth settings on part of the pattern.