Thanks RG, that makes it abit more clearer....
Britain did use 'pulses' in the War, it came in the form of 'Oboe', a name given to a ground-controlled blind-bombing device of unique accuracy....From 30,000 ft at speeds of over 300 mph, the average operational error was only 300 yds; for lower heights it was even less....
'Oboe', [named so, as one navigator thought the 'note' of the CHL set sounded like an oboe, and the name stuck], was a system using two stations each with a different role: one, the tracking station - code name 'Cat' - sent dot-dash signals to the pilot; - The other, the releasing station - code name 'Mouse' - measured the groundspeed of the aircraft, warned the navigator of the approx; time before bomb release and gave the release signal...Both stations operated on the same wavelength but used different pulse radio frequencies [PRFs]. A pulse repeater in the aircraft responded to both PRFs so each station could measure the aircraft's range independently...The purpose of the repeater was to boost the signals to increase the range...The track to the target was along an arc of the Circle of Constant Path Range passing through the point of bomb release [R/P] with the 'Cat' at the centre....To avoid jamming it was proposed to operate in the centimetre band and, to avoid German interference with the information sent to the crews, it was incorporated in the pulse frequencies.....As the 'beam' [technically it wasn't a beam in the accepted sense of the word, because of it's aural similarity it is referred to as a beam...] was an arc it was estimated that the average time for the pilot to settle on it and fly it accurately would be 10 mins. flying time....A position on the track, called point A, equal to 10 mins. fly-time, was measured back from the R/P, and given to the crews at briefing, together with the height and airspeed at which the run must be made...Height and airspeed were vitally important because they were part of the complicated formula to calculate the R/P, and were used to determine point A....The navigator's job was to get the aircraft to point A, 10 mins. before time on target...Each crew had their own call-sign and this was transmitted from both stations, so when they heard their own call-sign, then and only then, the nav switched-on the repeater....Almost immediately the pilot would receive dots or dashes, depending on which side of the track they were on...When he settled on the beam, he got an equi-signal tone, in other words, a steady note....depending on where he was in relation to the target, and he would receive Morse letters that indicated by code his drift and time to correct, to get on line for the target....Finally, he would receive the release signal, 5 dits and a 2.5 second dah, and when the navigator pressed the bomb-release, it automatically cut-out the aircraft transmitter, so the ground stations knew the exact time of release...He would then switch-off the transmitter as soon as possible after bombing, so the next aircraft could be called.....
Alot more was involved to get the system ironed-out, but that's the initial rudiments of 'Oboe', and they started this around late 1941.....In time, to extend it's range, it was fitted into high-flying pressurised Wellingtons, and eventually in Mosquitos, about July 1942, so they could bomb right over to Berlin and other distant targets...It's value was huge to Bomber Command, along with the aid , H2S, that allowed them to bomb through cloud, and alot of this work was created in parallel with the US, both swapping valves and sets etc., to forward the accuracy and volume of the bombing of Germany.........