GB907554A - Improvements in or relating to aircraft altimeters - Google Patents

Abstract

907,554. Echo sounding. REUMERMAN, T., and HELMIG, W. H. T. Feb. 24, 1959 [Feb. 26, 1958], No. 6269/58. Class 40 (7). In an altimeter emitting a modulated radiation and determining height by a determination of the time interval between the emitted signals and received echo signals, the repetition frequency of the modulation pattern is caused to vary in dependence on the height. Fig. 1 shows an acoustic (or supersonic) embodiment in which an emitter SE is fed with short duration pulses from generator SG. At the same time, as a pulse is transmitted a series of flip-flop circuits F11, F12, F13, &c. is triggered to cause each circuit to change to its unstable state. The circuits are graded so that after a given time F11 returns to its original state, followed in sequence by F12, F13, and so on. Each flipflop circuit has an associated gate circuit P11, P12, P13, &c. which it tends to open, when triggered, by the connection over lines such as 24. However, each triggered circuit also inhibits the opening of any following gate circuit by applying a suitable potential to the line system 25; the gates are thus opened one at a time in sequence, P11 being opened first, P12 opening between the times when F1 and F12 return to their original states, and so on. Returning echo pulses are received at R, rectified at G2 and applied to line 26. The echo pulse on line 26 passes through whichever gate circuit is open to reverse one of control circuits F21, F22, F23 ... and light the appropriate indicator lamp L. The control circuits are interconnected so that operation of one automatically resets any previously operated member of the series. The output of G2 is also fed through delay means D1 to reset all the flip-flop circuits and through further delay means D2 to trigger the generator SG and initiate a fresh transmitter pulse. In the absence of a trigger signal from D2 the generator provides pulses at time intervals corresponding to a height greater than the maximum range of the system.