Patent GB-625734-A (GB)
Title: Radio location indicating system
IPC: G01S5/08
Filed: 1946-06-06
Abstract: 625,734. Radio navigation. STANDARD TELEPHONES & CABLES Ltd. June 6, 1946, No. 17268. Convention date, June 30, 1945. [Class 40 (vii)] A radio system for indicating the relative position of a receiving point, e.g. an aircraft, with respect to a pair of fixed points and at least one other point, comprises two beacons rotated at different rates and having different distinguishing characteristics and at the. receiving point means for receiving energy from both said beacons and separating the energy into two channels responsive respectively to the distinguishing characteristics, a visual position indicator having scanning means defining a spot of small area and controlled by the selective response of the respective channels, the spot being illuminated by means controlled by the conjoint response of the two channels when the signals having the distinguishing charaeteristics are simultaneously received and means for illummating the spot in response to energy radiated from the other point when the beams are simultaneously received at the other point. Beacons 1, 2 rotated at different speeds transmit frequencies F1, F2 which after separation by filters 14, 15 control circuits 17, 18 to transmit pulses to synchronizing devices 19, 20 associated with motors 21, 22 driving discs 23, 24 formed with radial slots 25, 26. The discs 23, 24 are driven at speeds slightly greater than those of the beacons 1, 2 respectively and the pulses from the circuits 17, 18 effect the release of the discs after they have been arrested. When the frequencies F1, F2 are simultaneously received a selector circuit 27 which is responsive to the conjoint outputs of the devices 17, 18 passes an impulse to a circular lamp 29 so that the illuminated intersection of the slots 25, 26 indicates on a chart 30 the position of the aircraft relative to inverted positions on the chart corresponding to the positions of the beacons 1, 2. At the third point 3 such as a hill or other obstacle, the receiver includes filters 7, 8 responsive to frequencies F1, F2 and operating relays 9, 10 so that the simultaneous reception of the frequencies is effective to key a transmitter 4 to radiate a frequency F3. At the reception point this frequency is accepted by a filter 16 and passed through a subsidiary filter 35 to a circular lamp 31 which may be a distinctive colour. An additional location, such as 3, may be indicated by the transmission of a further frequency which is accepted by the filter 16 and selectively separated by a filter 34 to operate an associated lamp 32 having a different colour from that of lamp 29 or 31. The relative position and height of a second aircraft may be indicated by providing on the latter aircraft a transmitter 38, corresponding to the transmitter 4 at the fixed point 3, and arranged to radiate a frequency F3 which may be controlled by an altimeter 39. When the second aircraft receives the frequencies F1, F2 simultaneously an impulse from the selector 27 which may comprise a pair of relays similar to relays 9, 10, operates its transmitter 38 to radiate the appropriate frequency F3. The reception of this frequency by the filter 16 of the first aircraft is separated by the filters 34, 35 to operate the corresponding lamp 31, 32 indicated by its colour the altitude zone of the second aircraft in addition to its position as determined by the intersection of the slots 25, 26.