Patent GB-1073592-A (GB)
Title: Digital graphical display system
IPC: G06K15/22
Filed: 1963-12-11
Abstract: 1,073,592. Computer output. CALIFORNIA COMPUTER PRODUCTS Inc. Dee. 11, 1963 [Dec. 14, 1962], No. 49013/63. Heading G4A. The invention relates to means for linking a computer to a graphical output device. In Fig. 2 (not shown), a binary-coded pattern on four lines (I1 . . . I4) from a computer is stored in flip-flops (33 ... 36) the outputs of which are connected to AND-gates (58) to decode the pattern into a command for a digital incremental plotter, either " pen down " (on to the paper), " pen up," " paper advance" " (+x) "paper reverse " ( - x), " pen move right " (+y), " pen move left " ( - y) or either of the x commands in conjunction with either of the y commands. When the pattern enters the flip-flops (33 . . . 36), at least one of them changes to 1 thus triggering a first one-shot multivibrator (40) to firstly cause a short break in a signal level (SRQ) to the computer causing the computer to remove the input pattern (I1 . . . I4) and releasing it for further calculations and then trigger another one-shot (41) to reset the flip-flops (33 . . . 36) and also gates the plotter commands to the plotter (at 61) and enables a third oneshot (42) to respond to a " pen up " or " pen down " plotter command if present to trigger a fourth one-shot (43). When all multivibrator pulses have ended, i.e. after 5 ms. if only x and y commands are given and after 105 ms. if a " pen-up " or " pen-down " command is given, an AND-gate (31) allows a signal (SRP) when provided by the computer to gate (20. . . 23) the next binary-coded pattern from the computer into the flip-flops (33 ... 36). The above and next embodiments are respectively suitable for use with the International Business Machines computers 1401 and 1620. Fig. 4 (not shown) shows the second embodiment in which a five-bit pattern representing one of ten plotter commands as in the first embodiment is stored in silicon-controlled-rectifiers in the computer and transferred to output leads (F0 . . . F4) when a 24-volt level is applied to a line (67) connected to these leads, those siliconcontrolled-rectifiers storing 1 conducting when this level is present. Presence of a data pattern on the leads (F0 . . . F4) is detected by AND- gate (80) connected thereto to trigger a one-shot (74) which generates signals (PCB1 and P3, the latter after a 15 microsecond delay) for return to the computer, e.g. to let it continue, and provided a signal (EOL) from the computer is absent, gates (94) plotter commands, decoded (91) from the data pattern (F0 . . . F4) to the plotter. The one-shot (74) triggers another one-shot (75) to hold said line (67) at 0 volts thus rendering the silicon-controlled rectifiers non- conducting in preparation for transmitting the next five-bit pattern. If the plotter command is " pen-up " or " pen-down," further one-shots (76, 77) are triggered. Further triggering of the first one-shot (74) from said leads (F0 . . . F4) is prevented as long as any one-shot pulse is still present. At the end of a write-command, the computer provides a signal (EOL) from which signals (PCB1 and P3) are generated for feeding back to the computer. Figs. 5, 6 (not shown) show an embodiment suitable for use with an LGP-30 computer. Each of six outputs from the computer is coupled to a corresponding input to the plotter via a passive RC circuit (113). The computer stores each of six bits in a thryatron (such as 116), which conducts if 1 is stored. In this case, capacitors (122, 126, 127) discharge partially through the thyratron, triggering a one-shot (131) in the plotter. When the discharge current drops sufficiently, the thyratron, (116), is cut-off (until the next six-bit pattern) and the capacitors (122, 126, 127) recharge from a source (115). Figs. 7, 8 (not shown) show in block form a single computer (suitable ones named) feeding four plotters (one at a time), the plotters being selected in a fixed sequence or by special command signals from the computer. Arrangements may be made for the computer to output on magnetic tape, punched cards or tape, or at a printer, as an alternative. Application to the monitoring of chemical plant is mentioned.