Patent GB-946257-A (GB)
Title: Improvements in or relating to start-stop distortion analyzers
IPC: H04L25/04
Filed: 1961-03-20
Abstract: 946,257. Telegraphy; pulse circuits. TESLA, NARODNI PODNIK. March 20, 1961 [March 22, 1960], No. 10043/61. Headings H3P and H4P. An apparatus for the measurement of relative distortion of one or all pulses in a series of pulses forming a start-stop telegraph signal comprises a ring counter and a number of coincidence circuits. Each coincidence circuit receives at its input an output of the ring counter and potentials indicating the transition points (i.e. change from mark to space, and vice versa) of the pulses. The coincidence circuits are associated with means such that the numerical value of the relative distortion of a selected pulse-or more than one pulseis indicated. General operation, Figs. 1 and 3.-A trigger circuit S receives telegraph signals, line S, Fig. 3, and produces a square wave at each transition point. A differentiator Q derives negative-going pulses from the square waves, each of these pulses indicating the transition, line Q. The pulses from Q feed a control gate G and a selector gate W, the latter permitting only selected pulses to pass to coincidence circuits K1, K2, K3. Control gate G is enabled only when a counter Z4 is in its zero position and switch T is closed. The first pulse from Q then starts Z4 counting, lines K1-K8, and this action causes a measuring-pulse generator M to start, line M. The pulses M are counted in a 20-position ring counter Z1, Z2, Z3, each pulse appearing on the eleventh terminal of the counter causing counter Z4 to step by one, lines K2-K8. The ring counter outputs pass to the twenty coincidence circuits K1, K2, K3 and when a pulse M and a transition pulse Q coincide the corresponding circuit is actuated. Since each transition should occur when the ring counter is in its zero position, coincidence when the counter is in any other position indicates that distortion is present and the degree of that distortion. If switch T is closed, when counter 24 reaches its zero position again, generator M is stopped and a zeroing circuit N is operated, this returning the ring counter to rest. Detailed operation, Figs. 2a, 2b and 3.- Telegraph pulses, as in line S, pass via a transformer Tr to the input trigger circuit, comprising valve El on one anode of which appear rectangular positive-going pulses corresponding to the mark elements of the telegraph signal and on the other anode appear like pulses corresponding to space elements. These pulses are differentiated by C1, R5 and C2, R6 and appear at the output of E2 as short negativegoing pulses, line Q, at the transition points. Pulses Q pass to the selector gate, comprising E6, E13, and assumed for the present to be open for the whole of the telegraph signal, and to the control gate comprising E3. Counter De4 being in its zero state (discharge on the eighth electrode) and switch T being closed, valve E3 passes a pulse Q via an amplifier E4 to the first cathode of De4, line K1, the zero state discharge ceases, line K8 and E3 cuts off. The eighth cathode of De4 is connected to the grid of E7 which, with E8, forms the measuring- pulse generator. While De4 is in its zero state E7 conducts and builds up a field in choke T1, and when De4 starts to count E7 is cut off and oscillations are set up in the circuit T1, C7, C8. Cathode follower E8 gives feedback over R11 to maintain constant the amplitude of the oscillations. The oscillations are amplified and appear as pulses M at the anode of E9. Pulses M are counted in the twenty position ring counter Del, De2, De3, each electrode eleven pulse counted causing De4 to step on by one, lines K2-K8. Each position of the ring counter has associated therewith a coincidence circuit, comprising discharge tubes D1-D20. Negative transition pulses from E6 are passed to all the tubes D1-D20, and when a tube receives simultaneously a transition pulse and a voltage from a section of the ring counter it discharges. The tube anodes may be connected to electronic counters which indicate which of the tubes has been discharged and therefore the degree of distortion present. When De4 has passed through seven states to return to its zero state valve E7 becomes conductive again and the pulses M cease. Further, E3 is open, ready for the next transition pulse, and the zeroing circuit, comprising E14, E15 is operated. Valve E14 is a differentiating amplifier, and E15 a mono-stable trigger. The rise in potential as De4 reaches its zero state is differentiated to give a positive pulse on one grid of E14, resulting in a negative pulse at the corresponding anode, middle line of lines N. This pulse actuates the mono-stable trigger E15 to produce a pulse of fixed length, top line of lines N. The output of E15 passes to E14 which therefore gives a negative spike at its other anode, bottom line of lines N. The first and second pulses at the anodes of E14 return, respectively, counter De2 and counter De3 to zero. Should switch T be opened the measuring-pulse generator E7, E8 and the ring counter De1, De2, De3, both continue to operate. This situation may be required, for example, in order to test the frequency of the measuring pulse generator. The distortion is determined for all pulses received while selector gate E6 is open, i.e. while E13 has a positive voltage at its grid. Switch P connects the grid of E13 to positive voltage sources of various time intervals. Thus, to measure all pulses P is connected continuously to a source, while to measure one particular pulse it is connected to corresponding cathode of De4.