I/EC
REPORTS
Plans for fully mechanized mail sorting involve four synchronized operations
• Automatic segregating (prototype developed) • Automatic letter facing and canceling (prototype being field-tested) • Letter coding (still in research stage) • Automatic letter sorting (beyond prototype stage, 20 units being made for extended field trials)
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Then a second set of scanners determines whether the letter is facing in or out—depending upon whether the stamp is at the leading edge or trailing edge—and whether it is paid at the "deferred" rate with a 2d. (2-penny) stamp having one graphite strip. The 2d. rate is akin to third-class mail in the U. S. A "fully-paid" letter carries a 3d. stamp bearing two conductive strips. Other denominations also have two graphite lines (see picture below). Research on this mechanization began in 1937. Early machines, using photoelectric scanners to identify the stamps by color, did not prove practical. Other means of detection were considered or tried without
success : attaching strips or metallic foil to the stamps, impregnating the stamp paper with salt solution for electrical sensing, impregnating with ferric oxide for magnetic sensing, treating with zinc or aluminum powder, or using minutely radioactive paper. Finally the marksensing technique was evolved by printing graphite lines on the back of the stamps. By having a single line on 2d. stamps and two lines on others, different signals are sent to ALF's memory when its high-voltage metal probes complete an electrical circuit through the graphite lines. Thus, letters or cards bearing 2d. stamps are picked out and deferred while priority mail is sorted for immediate delivery.
