Patent GB-1077534-A (GB)
Title: Printing apparatus
IPC: H04L12/54
Filed: 1964-08-02
Abstract: 1,077,534. Electric digital data storage; printers. INTERNATIONAL BUSINESS MACHINES CORPORATION. Aug. 21, 1964 [Aug. 23, 1963], No. 34204/64. Headings G4C and G4H. A printer is controlled through three recirculatory stores. A computer controls 64 printers via three revolvers and a scanner-distributer. Each revolver comprises a section of magnetic drum (or disc) track forming, with a delay line, a recirculatory loop. Each printer has a continuously rotating typewheel (5 r.p.s.), and a magnetically sensed disc to produce " character arrival pulses," one as each character comes into printing position. In the scanner-distributer, clock-pulse-driven counters scan the printers in turn to route character arrival pulses from them to a terminal revolver (2,450 r.p.s.) and " print pulses " (causing print hammer actuation) from the terminal revolver to the printers. The terminal revolver has three bit positions for each printer and stores print pulses received from a synchronizing revolver until they can be executed as indicated by character pulses from the scanner-distributer, also stored in the terminal revolver. The character arrival pulses are stored in the terminal revolver until they can be sent to the synchronizing revolver at the appropriate time. The synchronizing revolver (350 r.p.s.) has a segment for each printer which stores a first and a reserve character to be printed and control bits. The characters are each in the form of a binary number specifying the distance of the character from the home position on the typewheel. The first character's number is decremented by one by each character arrival pulse relating to the destined printer, by logic which inverts the lowest order 1 and all lower orders 0's (lowest order bits first) as the number recirculates in the revolver. When the number reaches zero, a print pulse is sent to the terminal revolver, the reserve character is moved into the first character position by bypassing the delay line and a character request signal is sent to a data revolver. If no character is to be printed for a given revolution of a given typewheel, a set of all 1's is stored causing hammer actuation at the blank " home position " of the typewheel. The data revolver (10 r.p.s.) stores a 105-character block for each printer. It sends a character to the synchronizing revolver when requested by the latter and shifts the remaining characters in that block along by by-passing the delay line. When a given block has been thus emptied, a set of 1's ending the block is detected and the revolver enabled to accept another block from the computer. The data revolver may involve several drum tracks connected in series by reading and rewriting. Timing.-In Figs. 1, 2 (not shown), all timing is by clock pulses derived from timing tracks on the revolver drums. In a modification (Fig. 6, not shown), clock pulses from the computer are fed into a multi-tap delay line, the taps being connected to OR gates to produce some timing signals and to AND gates to produce others. The AND gates are enabled by a flip-flop which is set once every 35 times a clock pulse is fed into the delay line and reset by the output of the last of the AND gates. Keyboard input.-A magnetic distributer is mounted on each typewheel shaft to scan switches set by a keyboard so that each printer station can send a serial message to the computer, over the same line that carries the character arrival and print pulses. The message pulses and character arrival pulses overlap but only partly so that the increased pulse width when both are present allows separate detection.