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Aviation History
1958
1958 - 0656.PDF
672 AIR TRAFFICCONTROL. . . FLIGHT Left, two of the 28 cabinets which make up the AYCO Volscan. Operators are illuminating blips for automatic tracking. Carlson are probably the first manufacturers to have given seriousconsideration to the need for limited-application simple andlight- wcight mobile equipment. The purpose of their new LABIL—light aircraft binary information link—is self-explanatory. Data is entered into the link by the aircraft pilot or observer and trans-mitted automatically on demand from the ground via the voice channel of existing communications equipment. The unit operates in conjunction with any voice transmitter/receiver. The operator adjusts selector knobs (13 data categories, each covering from one to four figures, is the present transmissionlimit) and the message is stored in teletype code form until the transmit key is pressed in response to a message request signal— CCCCCCCCCRADAR DATA COMPUTER DATA O LINKS CONTROL SIGNALS APPROACH CONTROL LOCAL CONTROL CCALONG RANGESURVEILLANCE RADAR ADJACENT CONTROL CENTRES AUTO TRACKING RADAR COMPUTER -*[~MEM0RY DRUM (__ ^ . TOT? (DISPLAY DYNAMIC DISPLAY CONTROLLER (SJ as indicated by a panel lamp. Information could also be fed inautomatically from fligjtt instruments through transducers. The airborne unit is transistorized, measures 6in x lOin x 13in andweighs about 25 lb. The message as received on the ground is checked for error dueto noise interference and printed out by teletypewriter. Error sensing in the receiving unit is accomplished by transmitting eachcharacter over the link twice. The first character is stored in one register and the second version of the same character in another.A comparator examines the registers and converts each character into teletype form only if complete agreement is obtained. Messagetransmission with the present LABIL design occupies five seconds and printing-out 11. Characters failing this error check appear asblank spaces in the printed text and can thus be identified, since the probability of character rejection due to an error greatly exceedsthe rate at which undetected errors are passed. An error-rate check indicates the point at which the link is no longer useful dueto noise interference. Scope is provided within the system for requesting re-transmission of a message to fill-in omissions andto tell the airborne operator that the message has been received. Equipment for providing aircrews with teleprinted informationrelayed from ground sources is being built—initially in small quantities—by Standard Telephones and Cables in association withCreed and Co. The system is being evaluated by B.O.A.C., who have carried out trials over the North Atlantic (the first successfultest was made two years ago) using teleprinted weather information relayed from a station on each side of the ocean radiating about2 to 5 kW carrier power. The airborne equipment provides four crystal-controlled channels, in the 90-130 kc/s range and thereceiver will print with accuracy on input signals of one-third of a microvolt. The teleprinter operates at up to 100 words/min andweighs 35 lb. T.C.A. are evaluating similar systems using Federal Telecommunication Laboratories equipment. Air France andSwissair are about to start evaluation and Marconi also has an interest in this field. Competition for development contracts for automatic andsemi-automatic equipment for air traffic control has been very intense within the United States. The Airways ModernizationBoard has had a proportion of the C.A.A.'s operation and regula- tion budget—totalling £26.6m in 1957, £44.3m in 1958 and£62.5m in 1959—to spend on research and development of air Diagrammatic layout of the Dutch SATCO control system.
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