Patent GB-845115-A (GB)
Title: An electronic signal transmitter for a teleprinter
Inventor: SUSICKY STANISLAV
IPC: H04L25/40
Filed: 1957-01-16
Abstract: 845,115. Printing-telegraph transmitters. TESLA NARODNI PODNIK. Jan. 16, 1957, No. 1648/57. Class 40(3). An electronic teleprinter transmitter comprises a keyboard with a plurality of normally open key contacts connected to pre-determined pairs of a number of output terminals and a number of normally open control contacts each connected in series with a separate resistor across a pair of output conductors, a combination network comprising a plurality of impulse elements each connected to predetermined combinations of said output terminals, a memory circuit comprising a chain of bistable trigger devices each connected to the output of a separate one of said impulse elements, a locking circuit connected to the output of the final trigger device of the memory chain, a time base, and a coincidence gating circuit responsive to a change in resistance produced across said output conductors when only one of said control contacts is closed in response to the depression of its associated key, to a control impulse from said time base, and to a distinctive potential derived from said locking circuit when said last trigger device is in a predetermined stable state, to permit a registration impulse to pass to said combination network to produce impulses from preselected elements thereof according to the particular key depressed so as to change corresponding trigger devices in said memory circuit to their opposite stable states. The operation of a key of the keyboard closes two pairs of contacts of which the first pair via connections a, b and a resistor, such as R42, completely cuts off the valve El, Fig. 3, of which one triode is normally conducting, so that a positive pulse is fed to the valve E2 of a coincidence circuit. Control pulses from a time base operating at 50 c.p.s. are fed to the grid of E2 together with a pulse from a locking circuit comprising a valve E13, Fig. 5, when the seriesconnected memory circuit comprising valves E5 - E10 is in its normal or rest condition. The valve E2 rendered conducting in response to the simultaneous application of these three positive pulses changes over the valve E3 so that a negative pulse from its right-hand anode cuts off the valve E4 to pass a pulse selectively through the primary windings of transformers Tr1 - Tr6 connected in accordance with the actuated key and whose secondary windings are connected via terminals a, b, to the inputs of the trigger E10, corresponding to the start element, and triggers E5 - E9 associated with the information elements. The operation, for example, of the key carrying the letter X connects the inputs 6, 12 so that a pulse passes through the primary windings of transformers Tr2, Tr6 and pulses generated at the secondary windings are applied to terminals a, b designated 2 and 0 appertaining to valves E8, E10 of the stepping memory circuit E5 - E10. During the transmission of a character the locking circuit comprising the double triode E13  prevents the operation of the coincidence circuit, but the return of the trigger E10 to its normal condition allows the registration and transmission of a subsequent character, the timing pulses being operative to change over the trigger E10 to operate the valve E12 to send the start element and subsequently to step the condition of the triggers E9 - E5 as determined by the transformers Tr1 - Tr5 to control the trigger E10 to operate the valve E12 to transmit the appropriate code combination of impulses. Specification 826,148 is referred to.