Patent GB-923841-A (GB)
Title: Electronically controlled high speed printer
IPC: G06K15/06
Filed: 1959-09-02
Abstract: 923,841. Selective printing. SPERRY RAND CORPORATION. Sept. 2, 1959 [Sept. 17, 1958], No. 29994/59. Class 100 (4). [Also in Group XIX] A high-speed printer, for use with an electronic computer, comprises means for receiving and means for storing groups of impulses representing characters to be printed and an intermediate register for transferring said groups of impulses from the receiving to the storage means and for receiving said groups of impulses again from the storage means. The printer further comprises a device for generating impulses representing characters approaching printing position, a comparator comparing groups of impulses from said intermediate register with groups of impulses from said generator, coincidence resulting in printing of the required character. The printer can be controlled directly by a computer in which case all timing pulses originate in the computer. Alternatively the input may be from an intermediate storage device such as a magnetic tape in which case clock pulses in the printer control timing pulses in the tape unit. Connection to the computer or the tape unit is effected by manually-operated switches. Inputs from the tape unit or computer feed input register 21 comprising seven flip-flops. The characters may be alphabetic, numeric or symbolic, an excess-3 system with 7th parity position being used, as described in Specification 749,836. The information from the tape is supplied in parallel, that from the computer in series. When a character has been registered the register 21 acts as a shift register to transfer the character to buffer register 22, after which the character is transferred in parallel form to a magnetic core buffer memory 23. Memory 23 contains 840 cores in the form of a 12 x 10 x 7 matrix and can store a block of 120 characters which is equivalent to one line of printing. When the block is registered read-in stops and the information is transferred character-bycharacter through the buffer information register 22 to comparator 24. The type is arranged in longitudinal rows on a cylinder 18, there being 51 such rows. As each character arrives in printing position its code is generated at 19 and applied to register 25. It is applied for a minor cycle to comparator 24 and during this minor cycle is compared with each of the 120 characters stored in buffer memory 23. Whenever there is coincidence a signal is sent to address comparison matrix 26 to indicate the address of the corresponding character in buffer memory 23. The cycle is repeated as each line of type approaches printing position. Connected to the buffer memory 23 are two address generators 27, 28 which are respectively 12- and 10-position shift registers. When a character is entered in buffer memory 23 the X-address generator 27 shifts one position. After 12 steps carry takes place and Y-address generator 28 shifts one position. The outputs of 27 and 28 are applied to the address comparison matrix 26 which comprises 120 " And " gates. When identity is established between the character in printing position and a character applied from buffer memory 23 to the comparator the corresponding " And " gate in matrix 26 is energized to transfer information from address storage 29 through plugboard 31 to a check storage 32 and a print storage 33. A print control device 34 then clears the storage devices and primes the appropriate print thyratron 130. Rotating with type wheel 18 is a print index generator 17 comprising a succession of magnetic spots. When two spots corresponding to a row are sensed at the same time then toggle 36 is operated to fire the primed print thyratrons 130, so operating the appropriate hammers. Toggle 36 also drives a print index counter 37. When the counter has completed a count of 51 corresponding to the 51 lines of type on the wheel 18 it signals the end of a major print cycle. Buffer memory 23 is then cleared and the next block is read in. Checks.-Comparison counter 38 has two inputs, one from comparator 24 whenever identity is established and the other from buffer information register 22 whenever a character is transferred to the buffer memory. This ensures that all characters are subjected to comparison. Check circuit 41, fed by generators 27, 28 ensures that all 120 addresses in buffer memory 23 are identified and filled. Check storage 32 maintains a check on the number of addresses to be printed in a major print cycle. As each print core is set in storage 33 a print thyratron is primed. The resultant thyratron pulse clears the appropriate check core in 32. By the end of the cycle all cores in 32 should be clear. If this is not so an end-ofcycle pulse applied to 32 produces an error signal to stop printing. Format.-The format is determined by function table 42 and the setting of plugboard 31. Format information, not for printing, is applied by the computer or magnetic tape through registers 21, 22 to the function table 42. The plug-board permits variation of printing position. The function table controls the following circuits:- Multi-line control 43 controls the number of lines on which a block of 120 shall be printed. From 1 to 6 lines may be used, with or without repetition of some of the information. Control to fit a particular format is effected by a multiline counter 51 (the count of which is adjustable within the range 2-7 according to the setting of plugboard 31). Fast feed control 44 allows the paper to be fed rapidly whenever no printing is to occur. The rapid feed may extend for 2-132 lines and is effected by inhibiting paper stop pulses from a magnetic drum until a hole in an endless paper loop 55 is sensed. This loop has 7 channels. The length of paper without printing is determined by holes in the first four channels. A hole in the fifth channel indicates the beginning of fast feed which ends at the sensing of a hole in the sixth channel, indicative of the end of the form. The seventh channel establishes the homing position or beginning of the next form. Stop control 46 stops printing operations for a specified period of time. Class control 47 identifies and prints only preselected types of information. When one of the four class control characters is recognized, dependent on appropriate setting of the plugboard, the block containing that character is ignored and read-in of the next block ensues. Break-point control 48 is similar to stop control but is operative only when a particular break-point switch has been manually operated. Computer digit control 49 is used for test purposes and replaces non-print characters from the computer or magnetic tape by predetermined characters which are then printed on the next line. Paper feed control 54 provides for single-, double- or triple-line spacing. Spacing is determined directly by the computer, or by preselection on the plugboard in magnetic tape operations. Tape read-in control 58 and computer demand control 59 connect the print unit to the tape unit or computer, respectively. In on-line operations, when the computer is ready for a printing operation it signals the printer. If the printer is busy the operation is postponed. The demand signals are repeated until the printer is idle and returns an idle signal whereupon the computer signals computer demand control 59 to initiate printing. A similar arrangement exists in respect of the tape unit and control 58.