Patent GB-1107923-A (GB)
Title: Improvements in teleprinters or the like
IPC: H04L13/08
Filed: 1966-05-20
Abstract: 1,107,923. Telegraphy. CREED & CO. Ltd. 20 May, 1966 [20 May, 1965], No. 22575/66. Heading H4P. A mechanical drum store is used in a teleprinter transmitter to store a plurality of character combinations and comprises means for the automatic generation and insertion of case shift signals in the transmitted message. The store has a plurality of rows of radially movable studs 13, the studs of each row being positioned by a keyboard in accordance with the 5-unit signals to be transmitted. Each row comprises two further studs positioned in accordance with the case of each character, so the storage capacity for character combinations is independent of the number of inserted case-shift combinations. The drum is rotated, in the direction shown, by a Maltese cross stepped once for each character read in. The studs project through the drum and are sensed by electrical contacts which are driven, in the direction shown, through a friction clutch by drive wheel 15c. A cam resets the studs after sensing. The sensing unit can be driven in the opposite direction by engagement of a see-saw lever 19 with teeth 14a on the end of the drum. If the drum is filled to capacity the keyboard is locked. Read out, no change in case.-When one or more characters have been read in to the store it will have rotated away from its empty or rest position, carrying with it the sensing unit which is locked to its movement by the see-saw being in the position shown. The sensing unit rests with the five combination-sensing contacts intermediate adjacent rows of studs 13 and with its two case-sensing contacts sensing the caseshift studs. Because of the rotation of the drum locking member 18 will release lever 26, so allowing clutch 25 to engage and rotate the transmitter cam-set which includes cam 27. Cam 27 urges follower 22 and lever 21 clockwise so sliding collar 20a to the left and rocking see-saw 19 anticlockwise. The sensing unit then rotates anticlockwise until the lower leg of the see-saw engages a tooth 14a. The five sensing contacts now sense the storage studs, and a corresponding 5-unit signal is transmitted, together with Start and Stop bits. Cam 27 returns to the position shown, returning the see-saw 19 and allowing the sensing unit to take up the rest position prior to the next stored character. Insertion of case shift.-When the case shift studs indicate that a case shift combination must be inserted prior to transmission of the next character, magnet SM is energized, stepping ratchet 31a and allowing lever 32 to engage arm 21a. This arm is an extension of lever 21 and so prevents the sensing unit from sensing the stored character since the lever 21 is unable to free the see-saw from the engaged tooth 14a. Depending upon the position of one of the case shift studs one or the other case shift signal is sent, LTRS by reading the unactuated sensing contacts and FIGS by reading the unactuated contacts but reversing the third bit by the case shift stud. As the transmitter cam set rotates, contacts SK8 open and de-energize magnet SM. Lever 21 is thus released and the character stored is then transmitted as described above. The case-shift stud-setting mechanism, Fig. 4 (not shown), is designed to engage the studs only on the change in case, although each character combination from the keyboard is accompanied by a case-indicating movement of the case-shift bar.