Another type of barrage was the SOS barrage, fired in response to a German counterattack. An SOS barrage could be brought down by firing a flare signal of a pre arranged colour, as a German barrage tended to cut the telephone lines. A pre-registered barrage would then descend on No Man's Land. With the introduction of the tank the artillery was no longer required to aid the infantry by destroying obstacles and machine gun positions. Instead, the artillery assisted by neutralising the German artillery with Counter battery fire. British Army researchers under Lieutenant William Lawrence Bragg developed sound ranging, a method of determining the location of hostile artillery from the sound of its guns firing. A Counter Battery Staff Officer (CBSO) was appointed at each corps to co-ordinate the counter battery effort, collating reports from sound ranging and Royal Flying Corps observers. By the end of the war, it was realised that the important effect of the barrage was to demoralise and suppress the enemy, rather than physical destruction; a short, intense bombardment immediately followed by an infantry assault was more effective than the weeks of grinding bombardment used in 1916. The Royal Engineers Signal Service, formed in 1912, was given responsibility for communications that included signal dispatch, telegraph, telephone and later wireless communications, from army headquarters to brigade and down to battery level for the artillery. For most of the war, the Army's primary methods of communication were signal dispatch (employing runners, messengers on horseback, dogs, and carrier pigeons), visual signalling, telegraph, and telephone. At the start of the war, the Army had a small number of wireless sets, which in addition to being heavy and unreliable, operated on longwave. In 1915, trench wireless sets were introduced, but the transmissions were easily intercepted by the listening Germans. Civilian telephones were used at the outset of the war, but they were found to be unreliable in the damp, muddy conditions that prevailed. Consequently, the field telephone was designed; a device that operated with its own switchboard. Apart from voice communication, it featured a buzzer unit with a Morse code key, so that it could be used to send and receive coded messages. This facility proved useful when, in the midst of bombardment, exploding shells drowned out voice communication. The telephones were connected by lines that sustained continual damage as a result of shell fire and the movement of troops. The lines were generally buried, with redundant lines set in place to compensate for breakages. The primary types of visual signalling were Semaphore flags, lamps and flags, lamps and lights, and the heliograph.