Patent GB-1402065-A (GB)
Title: Apparatus for the visual display of inscriptions
IPC: G06K17/00
Filed: 1973-10-04
Abstract: 1402065 Optical projectors J J DAMLAMIAN 4 Oct 1973 [4 Oct 1972] 46368/73 Heading G2J [Also in Division G4] A device for projecting transparencies carrying at least one magnetic tape section having magnetically recorded thereon binary digital words representative of alphanumerical characters, and at the same time visually displaying the characters in alphanumerical form, comprises means for imparting to the transparency a constant velocity movement from a feed position to a projection position, a magnetic head co-operating with the tape section for selectively writing thereon or reading therefrom the binary digital words, a writing-in register and a reading-out register connected to the head, and a visual display panel connected to the reading-out register via a binaryword-to-visual-character converter, the registers and converter being controlled by a clockpulse generator synchronized with the movement imparting means. A magnetic tape section may be provided along each edge of the transparency, each with two tracks to record the same information in complementary NRZI forms for self-checking. The information in the upper and lower pairs of tracks are read or written (according to the setting of a record/playback key on a keyboard) simultaneously by two pairs of heads as the transparency moves between the feed position and the projection position, in one direction or the other. Information to be recorded is supplied by the keyboard via a write buffer register to the writing-in (shift) register, respective halves of which feed the respective pairs of heads, thus performing a parallel-to-serial conversion for the information in each half. The two heads of each pair are inter-connected by an inverter. Information read similarly goes to the two halves of a read buffer (shift) register which thus performs serial-to-parallel conversion, the buffer register feeding the reading-out register which controls the display panel (e.g. liquid crystal) via the converter as stated. The converter and display are also fed from the write buffer register. Actuation of a "normal-sorting" key on the keyboard causes comparison of the contents of the write buffer register (fed from the keyboard) with the contents of the reading-out register. A keyboard character which will give a compare equality with any character is available. Normally the supply of a motor moving the transparency is reversed every half-revolution of a drive pulley so as to move the transparency from the feed position to the projection position and back again, then repeat for the next transparency in the sequence, but equality in the comparison causes reversal after one revolution instead so that the transparency moves beyond the projection position to a position at which it is removed from the sequence. Thus keyboard-controlled sorting of transparencies on the basis of the magnetically-recorded information on the transparencies is performed. The transparency is moved between its various positions by being gripped between arms hanging from a trolley reciprocated back and forth inside a cross-beam of the apparatus by a cable around the drive pulley. In a modification, a manually-operated handle is used to drive the cable, the cable passing around a pulley connected to an eddy current brake and a toothed disc producing pulses from a magnetic sensor to synchronize the clockpulse generator controlling the electrical circuitry. In the motordriven case, similar arrangements are connected to the drive pulley.