Patent GB-938603-A (GB)
Title: Improvements in or relating to apparatus for checking printing in a high-speed printing machine
IPC: B41J29/393
Filed: 1961-06-05
Abstract: 938,603. Electric selective signalling systems. COMPAGNIE DES MACHINES BULL. June 5, 1961 [June 14, 1960], No. 20208/61. Class 40 (1). Apparatus for checking the printing of a highspeed printer connected to a computer and verifying that the printed characters coincide with the coded characters transmitted. by the computer, comprises a transducer device 23 emitting a pulse each time a striking device 13 has been actuated, a comparing device 10 for comparing the coded character transmitted by the computer with a coded character generated by a code generator 2 of the printer and for generating a comparing pulse in the case of character identity, so that emission of a comparing pulse which is not coincident with the emission of the pulse from the transducer device or vice versa produces the emission of an error signal. In the apparatus the printing circuits of the printer are connected to the computer by a channel 15, along which the characters to be printed are successively sent into an input register 7 and the coded characters comprise six binary digits together with a seventh accompanying binary digit known as " parity key" corresponding to a binary " 1 " if the number of " 1's " contained in the character is even and an a " 0 " if it is odd. As each character is introduced into the register 7 a control pulse is sent from a main control circuit 30, consisting of a succession of flip-flops connected one behind the other by logical " AND " and " OR " circuits, into a selection circuit 4, to select successive store lines of a memory store 3 consisting of a plane matrix comprising magnetic cores forming a network of 8 lines and 120 columns. The character written in the register 7 is transferred to the store 3 after passing through the register 8, checking of the parity key at 26, through a store writing circuit 5, whereupon each character is written in six cores, whilst the seventh contains the parity key and the eight is left in the state " 0," which state will be changed over to the state " 1" after printing and checking of the character. When the entire store is full the rotation of a type-wheel 1 effects the generation of the first coded character by the code generator 2, which character is written in the code register 9. The first character is also extracted from the store 3 by a reading circuit 6, written in an output register 8 and the two characters written in the registers 8 and 9 are compared in the comparing device 10, which emits an output signal in the case of character identity, resulting in a binary " 1 " being written in the first position of a register 11 consisting of 120 store cores, whereupon the character is re-written in the store 3. The same generated character is then compared with the 2nd, 3rd ... 120th characters extracted one-by-one from the store, sent to the register 8, compared at 10 and each time identity is detected a signal is sent to the register 11. When all the 120 characters have been tested a number of cores of the register 11 corresponding to the positions of the characters to be printed are in the state " 1" a " striking order " is given from an electronic clock 14 and a reading current from register 11 in the form of pulses is applied to print control amplifiers 12, which actuate the electromagnets of a striking device 13 acting on striking hammers corresponding to the positions of the first character to be printed. The second character is then generated, written at 9, the store read again and each character compared at 10 with that written at 9. The process continues until all the printing characters have been compared with the line characters and the line has been printed. This operation is synchronized by the rotation of the type wheel drum 1 carrying the types over 2/3 of the circumference only, i.e., over an angle alpha called the major cycle, the remainder of the cycle corresponding to an angle # (Fig. 5, not shown), being used for the paper feed between successive lines and filling of the store 3 with all the characters of the succeeding line, the respective instructions being sent from the computer into a line space control 33 and instruction register and analyser 31, 32. To check that the printed characters agree with the coded characters the displacement of the striking.hammers is used to vary the air gaps of the corresponding transducers 23, which generate checking signals following the response time of the striking mechanism and change the state of the same number of cores of a register 24, whereupon a binary " 1 " is written at a bit register 25. At the same time the coded character corresponding to the type just struck and which has been registered at 9, is applied to a delay circuit 22, which after a delay period corresponding to the response time of the striking mechanism sends it into a delayed code character register 21, whence it is transferred to a check comparator 20 receiving also the characters extracted from the store 3 following writing of the character in register 21, and passed from the comparator 10. If identity is found in 20 a gate 27 emits a binary " 1 " signal via its " AND " circuit, which controls the re-writing of the character in the store 3. The character is sent to the modifier circuit 28, where the seventh and eighth positions are modified, because a binary " 1 " is entered in the eighth position, the registration indicating that the character printed has been checked and found satisfactory. As a consequence the parity key is reversed and the seventh position is also modified. When the complete line has been printed and checked all the 120 cores of the eighth column of the store 3 contain a binary " 1 " in the location of the original " 0 " and the instant when all cores are in the state " 1 " is determined by a scanning circuit 29, which then initiates the paper jump and the despatch of the 120 characters of the succeeding line. If there is no identity found at the check comparator 20, the gate 27 indicates via an " OR " circuit the case of an error in appropriate visual indicating systems. Specification 907,479 is referred to.