Patent GB-475013-A (GB)
Title: Improvements in or relating to synchronising arrangements for picture transmission systems, teleprinters and telewriters
IPC: H04L21/00
Filed: 1937-02-05
Abstract: 475,013. Synchronous movements. SIEMENS & HALSKE AKT.-GES. Feb. 5, 1937, No. 3529. Convention date, Feb. 5, 1936. [Class 40 (iii)] The spindles of copying or facsimile printing- telegraph transmitters and receivers are driven at approximately the same speed, are stopped after each revolution, and are set in rotation by a starting-impulse with such different retardation periods that the apparatus which is started earlier reaches with certainty the position of rest before the next starting- impulse. Each station comprises a combined transmitter and receiver which, together with the paper feed, may be set in operation from the drive through a common coupling, Figs. 1 and 2 (not shown). Actuation of a character key 60 closes a contact 63 to transmit a starting- impulse in the period of a spacing scanning line between consecutive characters. Alternatively, the impulse is transmitted by a cam on the drum carrying the character cams 64, Fig. 1 (not shown). The key also opens contacts 70 to switch in circuit an inductance 69 which retards the release of the transmitter by an electromagnet 68. The key may be locked until the end of the transmission of a character, Fig. 4 (not shown). Avoiding accidental duplication of characters. So long as the key remains depressed, a mechanical lock 72, 74, 73a, which is held in operation by an abutment 73 on the key, stops the transmitting drum before the initial position is reached. Another part 66, 77 locks the intermediate lever 61 of the actuated key, while the part 72 prevents a second depression of the key of which the intermediate lever is in the operated position. According to a modification, the armature of the coupling magnet 68 is so shaped that it can also arrest the stop 75 before the initial position of the drum is reached, and the circuit of the coupling magnet is kept open so long as the actuated key remains depressed, Fig. 6 (not shown). The transmitter is started by the local receiver opening a shortcircuiting contact, which a series cam-actuated contact renders effective only at the position of rest. Preventing the recording of the starting- impulses. The receiver is switched off for the duration of the impulse, or the spindle accommodates as many helical ribs as there are scanning lines to a character, including the spacing line, and only the ribs for printing the actual character are provided, Fig. 7 (not shown). Alternatively, one of two intermeshing helical gears rotates at the speed of the transmitting-drum and has the teeth on a portion of its circumference replaced by a straight circumferential guide tooth for the second gear-wheel which drives the recording spindle, Fig. 8 (not shown). This stops the spindle during the inter-character space whilst the point of contact between the spindle and the recording base is outside the part of the recording strip used for the characters. The feed of the paper is temporarily accelerated during the inter-character space to give a greater spacing of the characters.