Patent GB-735117-A (GB)
Title: Improvements in or relating to printing telegraph apparatus
Inventor: PRIOR HECTOR THOMAS
IPC: H04L12/26
Filed: 1952-06-26
Abstract: 735,117. Testing-apparatus for telegraphy. STANDARD TELEPHONES & CABLES, Ltd. June 19, 1953 [June 26, 1952], No. 16078/52. Class 40 (3). An arrangement for measuring the distortion of telegraph signals, constituted by periods of marking and spacing potentials according to a code and separated by transitions, comprises means for receiving the electrical wave after transmission over a line or channel, a plurality of indicating lamps primed in turn for successive periods of time and means controlled by a transition of the received wave for applying an operating potential simultaneously to all the lamps in such manner that only the particular lamp which is primed at the time of arrival of the transition will be caused to glow. The arrangement is described for five-unit code signals with a speed of 50 Bauds, i.e. an element period of 20 ms., and one embodiment is arranged to indicate errors of 10 ms. in steps of 1 ms. A modification, Figs. 7, 8 (not shown) is arranged to show the distortion on an expanded scale and provided indications within limits 1 per cent in lieu of 5 per cent in the other embodiment. In the arrangement, Figs. 5, 6, counting circuits C3, C6 are arranged to produce 5 pulses of 200 ms. and 10 pulses of 20 ms. respectively whilst circuits C4, C5 each produce ten pulses of 1 ms. and are operated in sequence to produce an interval of 20 ms., all the counters being preferably as described in Specification 692,411. The basic timing pulses P applied to the various gates G, which are preferably' of the form described in Specification 636,700, [Group XL (c)], are derived from a generator 03 which provides pulses at 5000 per second, the pulses being of length 15 Ás. spaced at 200 Ás. In the inoperative condition tube SZ of the switching circuit FF is fired and the generation of the start impulse by a quantizer QC to the terminal T of which the incoming wave is applied, opens, on the occurrence of a +P pulse, a gate G10 which thereupon opens gate G11 and fires the start tube ST which in combination with the next - P pulse opens gate G3 and sets the counting chains C3, C4, C5 and C6 into operation. After 10 ms. steps of the counter C4, gate G5 is fired to operate stage MI of changeover device F4 and the pulses from C3 are fed to counter C5 for a further 10 ms. at the end of which gate G7 is fired to operate the stage MA of switch device F4 and to operate G8 so that the counting circuit C6 makes the first of its 20 ms. steps, the counting chains operating until the end of a code combination and until the device FF is set by triggering the stage SZ by a pulse derived from gate G12 in response to a stop or mark impulse M, a pulse +P and a pulse derived from the counting circuits C3, C5, C6 fixing an instant 138 ms. after the beginning of the start element of the original combination. The firing of stage SZ operates a circuit RC generating a resetting pulse R which is applied to the counters C3, C4, C5, C6 at the stages indicated. 10 ms. after the beginning of the start impulse a gate G18 is opened to operate stage FO of a change-over device F5 which is reset at the end of 130 ms. by a +P pulse and impulses from the counting circuits C3, C4 and C6. When the stage FO is fired a gate G9 is opened by mark, space or mark and space transitions according to the position of the switch SW, passed over a lead W to a flip-flop device FPI of which the stage FPA is normally off and the stage FPB normally on, and providing a potential bias via amplifier A4 so that the lamps are unable to glow. When the stage FPA is operated by a transition, the amplifier A3 changes the bias on all the lamps of the bank RN so that the lamp to which an impulse is being applied from the counter C4 or C5 glows and indicates the early or late percentage distortion of the transition. The circuit returns to normal with FPB triggered after a predetermined delay which determines the period during which the lamp remain illuminated. The lamp relating to zero distortion is operated by a gate G15 fed with pulses from stage MA of the switch device F4 and the zero stage of counting circuit C4, whilst the lamps indicating  10 ms. distortion are energized by gates G16, G17 fed by pulses from the stage M1 of the device F4 and the zero stage of the counting circuit C5 corresponding to a lapse of 10 ms. after the beginning of the start element and at intervals of 20 ms. until the cutting off of the counter circuits. If a spacing signal persists beyond the length of the normzl signal combination, the pulses from S, +P and those from the counting circuits C3, C4, C5 defining an instant 130 ms. after the commencement of the start signal, open a gate G13 to trigger the stage LS of the switching circuit FF so that the counting circuits cannot be set into operation. The reversion to mark in combination with a +P pulse opens gate G14 and gate G11 to operate stage ST so that the counting circuit operates for one cycle and then subsequently responds to the normal code combinations beginning with a starting element. In the modification, Figs. 7, 8 (not shown), the scale of distortion is expanded and the counting circuits are arranged to produce subdivisions of the 1 ms. range with fiveposition switches to indicate the sub-interval in which the distortion occurs. Two additional lamps are included to indicate whether the distortion is in a sub-interval earlier or later than the zone under consideration. The quantitizing circuit QC indicated in Fig. 6, is shown in Fig. 9, and comprises two interconnected valves V1, V2, the valve V2 being normally conducting and V1 non-conducting so that a high potential exists on the line m. The input waveform at terminal T is applied to the valves V1, V2 through gates comprising symmetrical, but oppositely polarized sets of rectifiers X5 . . . X9 and X10 ... X14. Rectifiers X6, X7 are jointly connected to a positive terminal S1 and individually through resistors R6, R7 to the negative terminal S2, the upper ends of R6 ... R7 being connected through rectifiers X8, X9 to an earth terminal E. Under these conditions rectifiers X6, X7 are unblocked and with rectifiers X8, X9 oppositely directed to X6, X7 the upper ends of resistors R6, R7 are substantially at earth potential. The values of resistors R5, R6, R7 are such that, in the absence of the rectifiers X8, X9, the upper ends of resistors R6, R7 would be slightly negative to earth. The associated rectifiers X11 ... X13 are similarly connected, and the values of resistors R8 to R10 are chosen so that in the absence of the rectifiers X13, X14, the potential, the lower ends of resistors R9, R10 would be slightly positive to earth. The positive and negative potentials at the terminal T are applied via rectifiers X5, X10 to the respective gates. An intermediate point on the resistor R15 in the grid input circuit of the valve V1 is connected by a resistor R20 to the junction point of the rectifiers X6, X7 and via resistor R21 to the junction point of the rectifiers X11, X12. Pulses P are applied simultaneously and at intervals of 200 Ás. via capacitors Q5, Q6 to the junction points of X7, X9 and X12, X14 respectively. When negative, marking potential is applied to T, valve V1 is cut off and the +P pulses applied to capacitor Q5 can have no effect since the rectifier X6 is conducting and holds the left-hand terminal of R20 at approximately ground potential. When the mark to space transition occurs rectifier X6 is blocked, but rectifier X7 is still conducting and holds valve V1 non-conducting. On the occurrence of the next +P impulse X7 is also blocked and the simultaneous blocking causes an increase of the potential applied to the grid of the valve V1 which conducts, cuts off V2 and applies an increased potential to the line s. Also rectifier X10 is now blocked so that rectifier X11 will conduct and hold the left-hand terminal of resistor R21 at earth potential and the - P pulses applied over capacitor Q6 have no effect. The occurrence of the next space to mark transition blocks rectifier X5, unblocks rectifier X10, thus blocking rectifier X11 and permitting the next - P pulse to block rectifier X12. The potential applied to the grid of valve V1 becomes negative and the circuit is triggered so that V2 conducts. The positive pulses appearing on conductors m, s are differentiated by capacitors Q7, Q8 in series respectively with resistors R22, R23 and R24, R25. A switch SW can be moved to one of three positions in which positive triggering pulses are sent over a line W in response to space to mark, mark to space, or both kinds of transitions. With the switch in either of the outer positions, the differentiated impulses from the other line are blocked by rectifiers X13, X14. When the switch is in its central position, the negative impulse which occurs on one line when a positive impulse occurs on the other is blocked by the corresponding rectifier X13 or X14. Specification 692,436, [Group XIX], also is referred to.