Patent GB-1318185-A (GB)
Title: Bank-note detector
IPC: G07D7/00
Filed: 1969-07-07
Abstract: 1318185 Banknote validator BRECKNELLREDCLIFFE ELECTRONICS Ltd 5 June 1970 [7 July 1969] 34225/69 Heading G4X [Also in Division G1] A banknote validator comprises photo-electric apparatus which measures the light transmission (optical density) and colour of the note at various parts of its surface and discriminator and gating circuitry to give an output only if the note is acceptable according to predetermined criteria. This apparatus is associated with a device for detecting the presence of an inset silver strip in the banknote. A gating circuit is provided to receive the outputs of the latter device and the photo-electric detector to give an output only when both the optical and the strip tests are satisfied. A drawer for delivery of the note to the test station is described Fig. 2. Photo-electric evaluation.-In a particular arrangement described with reference to the circuit diagram of Fig. 1 (not shown), five areas of the note are examined. A single lamp may illuminate all the areas of the note or individual lamps may be provided for each area. A photoresistor, photo-voltage device or phototransistor detects the transmitted light, there being provided in the respective paths: a neutral or grey filter (for monitoring a white area); two red filters (for two reds or brown areas); two green filters (for two green areas). In a modification utilized with the drawer of Fig. 2 there are six monitored areas and corresponding photoelectric stations using: red and green filters (for two dark green areas); a red filter (for a light blue/green area); a green filter (for a light blue/ green/brown area); a green filter (for a medium density green area); a neutral filter (for a white area used for compensating for soiled notes by adjusting the supply to the other five photo-cells). Each photo-cell is coupled via transistors to Schmitt triggers setting the upper and lower amplitude acceptance levels for that station. The triggers feed a system of AND-gates and a locking gate circuit. Silver strip detector.-When the note is in the test position a central transmitter electrode is positioned over the strip and this is supplied by a crystal controlled transistor oscillator delivering at about 27 MHz. Induced currents in the strip are picked up by receiver electrodes, two being provided, each spaced about half an inch from the end of the strip, in case of breaks in the strip. The received signals are fed to mixer transistor, the output of which is filtered, amplified detected and fed to an output transistor coupled to a locking gate circuit. Insertion of banknote.-The note may be conveyed by bands or rollers, triggered by a photo-electric presence sensor, which may continue (for acceptance) or reverse (for rejection) after the stationary test period. Alternatively, the user himself inserts the note into the test position by means of a flapped drawer, Fig. 2. A microswitch senses this insertion and starts the tests. If the note passes these within a predetermined timed period, a plunger plate pushes the noted down through a slot in its supporting plate. If it does not, a spring bias returns the drawer to its rest position for removal of the note by the user. An indicator (good or bad note) may be provided.