Patent GB-926714-A (GB)
Title: Improvements in the control of serial printing apparatus
Inventor: DIRKS GERHARD
IPC: G06K3/00
Filed: 1959-01-16
Abstract: 926,714. Magnetic drum data-stores. INTERNATIONAL COMPUTERS & TABULATORS Ltd. Jan. 14, 1960 [Jan. 16, 1959], No. 1655/59. Class 106 (1). The format in which data from an information track 11 of a magnetic drum is printed is controlled by a programme unit 31 which may suppress the printing of 0's to the left of the most significant digit of a number, or of a 0 in the tens-of-shillings position of a sterling amount, for example. The data is transferred from a track 11 selected by the unit 31 to an output buffer track 8, usually in a co-called " slow transfer " taking two drum revolutions, in the first of which the track 11 is examined before the transfer in modified form takes place. Data is recorded on the drum in interlaced form, as described in Specification 847,961; each track 11 can contain five words each having one character (decimal digit or other symbol) recorded in each of sixteen sectors. The sectors each have ten sub-sectors of which four are used for binary coded decimal digits and others have check digits and code bits for symbols. The timing signals used for format control are stored on tracks 43, 28 and 35, and comprise " start of revolution " (track 43), " end of sector " (track 28), and first and fifth sub-sector signals (heads 36 and 37) the last two indicating the start and end of the reading of those bits which are used for decimal digits. Hence flip-flop 34 is set for only these first four sub-sectors, and it is used to gate the output from a selected head 29 through 33 to a flipflop 24 which remains unset while zeros are being read, allowing end-of-sector pulses to be counted into a four-stage counter 26, but is set by the first non-zero digit to shut off sector pulses and reset 26 to zero. When reading of the word in 11 is complete 26 will register the count of any zeros occurring after the last non-zero digit, that is at the most significant end of the word. For the second drum revolution of a slow transfer 42 is set by a pulse from 43 to close gate 33 so that 24 remains unset, and 26 is counted up to 16 by pulses from 28, when a carry pulse sets flip-flop 40 (at the end of the sector containing the last non-zero digit) to close a gate 39 in the path (38, 39, 49, 50, 51) between the track 11 and output track 8. Print out from track 8 can then take place; this is effected by passing to a decoder 7 for each position of the print head 4 along a line data signals from a sector of the drum selected for that position by plugboard connections 22. These plugged connections enable in turn gates 17, which receive trains of clock pulses in the various sectors, as the print head moves along the paper, and each train gates the appropriate sector data to decoder 7 for printing. A character is printed for each two revolutions of the drum (the screwed rod 5 may be geared to the drum). Suppression of zeros to the right of the least significant digit is effected by unit 31 supplying signals over lines 52 and 53 to set 40 and open gates 54 and 55. The first non- zero digit (gated at 33, as before, by flip-flop 34) then unsets 40 to open gate 39 and the rest of the data word is re-recorded on another track 11 through gate 55. In a similar way a zero in specified position may be suppressed by setting 40 over 52 and unsetting it over 57 (if not unset by a non-zero character) at the beginning and end of the appropriate sector. Symbols for printing may be passed to the track 8 for recording in sectors 14 and 15 (it is assumed that no data for printing is stored in these sectors of tracks 11, and a flip-flop 67 closes gate 38 during these sectors); ten of these symbols are stored in sectors 14 and 15 of a track 58 and ten gates 62 (two only are shown), each receive an appropriate sector train and interlaced clock pulse train of pulses. Plug connections 61 enable one symbol from each sector to be routed via 65, 62, 66, 50 and 51 to the track 8, and these may be printed in desired positions by means of the connections 22. Instead of connections 22 permanent connections may be provided where a constant format is used, and in this case spaces in the required line of print which do not exist in track 11 may be inserted in track 8 by switching between a number of spaced heads 23; this arrangement would also allow insertion of punctuation symbols from another track. Specifications 851,752 and 900,481 also are referred to.