Patent GB-1103171-A (GB)
Title: Improvements in or relating to teleprinters
IPC: H04L1/00
Filed: 1965-12-10
Abstract: 1,103,171. Selective printing. SIEMENS A.G. 10 Dec., 1965 [11 Dec., 1964], No. 52532/65. Heading B6F. [Also in Division H4] In a teleprinter in which each received character signal comprises information bits and a parity bit, the parity of the type lever selected by the information bits is compared mechanically with the received parity bit, and printing of that character inhibited if necessary. In one embodiment, Fig. 1, the information bits select the draw-bar 4 of the character to be printed by means of selector segments and the parity bit energizes magnet 3 in order to set a parity segment 2. The parity segment 4 is notched to permit operation of the draw-bar only if the parity of the character associated with the draw-bar is the same as that indicated by the position of the parity segment, i.e. the received parity bit. In this embodiment each character signal also has two case shift bits, placing the type basket in one of the three case shift positions indicated. The sliding of bar 12 in slot 11 has the effect that the parity represented by operation of magnet 3 differs in the top case position from that in the lower two case positions. Reference is made to the electrical reversal of the effect of the parity bit, in accordance with case shift, and to the use of two magnets, each of which locks one half of the type levers. When parity error is detected an error symbol is printed either at the end of the line, Fig. 2, or at the position of the erroneous character, Fig. 3. In the former ease, when a selected draw-bar 25 is locked, e.g. by the arrangement of Fig. 1, it cannot be moved rearwards by the action of cam 21a and associated linkage. Cam 21b causes T-lever 29 to move forwards, taking draw-bar 35 with it. When arm 29b hits a stop 38, arm 29a disengages from type lever 37 which prints an error character, under action of spring 36. However, if no parity error is detected, rearward movement of the draw-bar 25 rotates rod 32 anti-clockwise and arm 33 disengages arm 29a from draw-bar 35, so preventing printing of an error character. Printing at the position of the erroneous character is performed by an arrangement, Fig. 3, which always permits operation of a selected type lever but which, when a parity error is detected, interposes a leaf-spring 61 which carries resilient material on one side and on the other an error character, which is thus printed. The position of the parity segment 41 is set by movement of the selected draw-bar 43 against a tooth 41b or against no tooth. This action positions locking rod 48 which is also positioned by parity bit magnet 56. If the position of the parity segment and the parity bit magnet agree, one or other of stops 48b, 48c will abut draw-bar 59, preventing its operation. Printing of a character then takes place. However, if they do not agree, the drawbar 59 is moved leftwards, raising the leafspring 61, interposing it between the paper and the type hammer 64. In each embodiment, the type basket moves along the print line. A mechanism for ensuring that case shift does not effect theparity position of the parity segment comprises means for displacing the pivot point of the lever moving the parity segment, Fig. 7 and 8 (neither shown).