Patent GB-1006911-A (GB)
Title: Improvements in facsimile systems
IPC: H04N1/419
Filed: 1964-04-04
Abstract: 1,006,911. Picture transmission systems. INTERNATIONAL BUSINESS MACHINES CORPORATION. April 4, 1963 [April 4, 1962], No. 13326/63. Heading H4F. A facsimile system for transmitting graphical information represented on a record medium (e.g. visual, magnetic or electrostatic) by a pattern of recordings of two kinds, the area occupied by recordings of one kind exceeding that occupied by the recordings of the other kind (i.e. the information is for example of the character of a graph or trace in black on a light background) comprises scanning means adapted to develop a sequence of electrical signals each representing the kind of recording in a different one of a number of elementary areas together making up a recording area on the medium, a counter responsive to said signals so as to produce an electrical output representing the number of successive elemental areas bearing recordings of said one kind preceding each elemental area bearing information of said other kind in a sequence of scanning, a multiple position data store connected to receive the electrical outputs as they are produced by said counter, means for transmitting the contents of a number of positions of said store to a receiving device in the form of electrical signals representing a number of said electrical outputs and means at said receiving device for developing a graphical image from the contents so transmitted. In Fig. 1, a pulse generator 1 supplies timing pulses to a scanning device 2 to cause its scanning motion to progress one increment along a scanning row for each pulse. A seven-stage cyclic binary counter, the secondary counter, supplies an output from an AND gate 6 to condition another AND gate 7 such that for count state 127 (starting from 0) the next pulse generator 1 causes the scanning device to start scanning the next row. The graphical information to be transmitted is thus scanned in a succession of parallel rows each formed of 128 elemental areas of which (see below) only 127 are used. The output from the AND gate 6 is also connected via an OR gate 5 to a second seven-stage binary counter, the primary counter, as also to an output 2a of the scanner 2 which is energized whenever the scanner detects a " black line ". The primary counter normally advances by one on receipt of each pulse from the pulse generator 1, but whenever it is energized from the OR gate 5 its count content is transferred to a store 3, and another AND gate 4 is conditioned so that the next pulse from the pulse generator 1 causes the counter to be re-set to zero. Thus in successive locations of the store 3 there are set binary representations of the number of " white " scanning increments between the " black " lines in each row, together with whatever binary count is registered in the counter P at the end of a row. The store 3 may comprise a magnetic core assembly or a punched tape or card arrangement. Reproduction of the image on the face of a C.R.T. 2<SP>1</SP>, Fig. 2, involves the sequential transference from a store 3<SP>1</SP> to a seven-stage binary primary counter of the 127's complement of the numbers stored in the store 3 of the recording apparatus. After the primary counter has been set to the 127's complement of a number of " white " increments to precede a " black " element or the end of a row, the counter is stepped by pulses from a pulse generator 1<SP>1</SP> which also cause the horizontal scan 2<SP>1</SP>a of the C.R.T. to progress. When the number of pulses applied to the counter is equal to the number of " white " increments the content of the counter is 127 so that the output of an AND gate 8 is energized and this causes the C.R.T. trace to be brightened by a device 2<SP>1</SP>c, provided that the contents of a secondary counter is not 127 at that time. When the contents of the secondary counter is less than 127 there is no output supplied from an AND gate 6<SP>1</SP> to an invertor 10 and a gate 9 is thus enabled to pass the output of the gate 8 to cause trace brightening. When the content of the secondary counter equals 127 (corresponding to the end of a scanned row) brightening of the trace is inhibited because the gate 9 is disabled. This prevents the production of a spot by the C.R.T. in response to store contents due to the end of row. Another gate 7<SP>1</SP> is then enabled to pass the next pulse from the pulse generator 1<SP>1</SP> to effect one step of vertical scan for the next horizontal scan row. The store 3<SP>1</SP> need not contain the whole of the contents of store 3 relating to a scanned image; it may be either a buffer store to hold one seven bit number or be formed merely of complementing circuit connected via parallel transmission circuits to the store 3 of the image transmitter. Other embodiments are described, Figs. 3-5 (not shown), wherein the entries made in the store correspond to only a fraction, e.g. one-half of a row, or a plurality of rows. Depending on the number of black elements per row this may lead to an economy of the number of storage elements required. Reference is also made (without giving details) to the use of scanning based on concentric tracks or spirals.