Patent GB-680301-A (GB)
Title: Improvements in or relating to electric signalling systems by means of position modulated pulses
IPC: G08C19/24
Filed: 1950-03-03
Abstract: 680,301. Electric selective signalling. GLOESS, P. F. M. March 3. 1950 [March 11, 1949], No. 5414/50. Class 40 (i) [Also in Group XL (c)] Apparatus for automatically controlling the position of an electric motor or meter in accordance with the time interval between a recurrent reference pulse and a recurrent position pulse comprises an artificial line to which the reference pulses are applied and having an electro-static pick-off driven by the motor or meter over the line to produce a recurrent pulse whose lack of coincidence with the position pulse produces a current to drive the motor or meter until coincidence occurs. As shown in Fig. 1, the received signal comprises a recurrent group consisting of a reference signal comprising two pulses O 1  O 2 , and an intelligence signal P whose distance from O 1 , O 2  is in accordance with intelligence to be transmitted. The recurrent train is applied from 11 directly to grid 23 of valve 13 and over a delay device 12 to grid 24, the delay device producing coincidence between the second and first pulses of the reference signal to make valve 13 conductive to pass a pulse O 2 . This derived pulse is applied to multi-vibrator 28, 29 to make the right-hand triode non-conducting and the left-hand triode conducting, so that the signal P, applied from 11 over valve 27, reverses the multi-vibrator to produce a pulse 31 whose length is proportioned to the distance O 1  O 2 -P and whose initiation is dependent on the pulse O 2 . The pulse O 2  is also applied to a delay line 8, 10 having a movable pick-off 2 which supplies a delayed pulse R over valve 19 to grid 18 of valve 15, the grid 17 being fed with the pulse 31. If the pulse R lies within pulse 31, the valve 15 conducts to provide a current smoothed by condenser 16 for actuating the moving coil K and thus moving the pick-off 2. The pick-off thus traverses the delay line until pulse R just fails to lie within pulse 31, and the pickoff pointer 1 thus attains a position corresponding to the transmitted intelligence. In Fig. 5, the received signal comprises a recurrent group 40 consisting of a reference signal O Fig. 6 and the three intelligence signals 41, 42, 43 which can each occur anywhere in the indicated ranges L, B. J. This signal is applied at 11 to a separating circuit S, similar to S of Fig. 1, which isolates the reference signal and applies it to the delay lines in devices G', G<SP>2</SP>, G<SP>3</SP> in series, these devices corresponding to the device G of Fig. 1. The isolated reference pulse is also applied to apparatus W, similar to the apparatus W of Fig. 1, to produce a pulse whose length corresponds to O<SP>2</SP>-41 Fig. 6; this pulse is applied to L<SP>1</SP>, L<SP>2</SP>, L<SP>3</SP>, which are similar to L of Fig. 1, but is effective only in L', so that the pick-off of G' is positioned in accordance with the position of signal 41. The pulse O<SP>2</SP> after passing through G' is applied to G<SP>2</SP> and over a link network N to device W to produce a pulse whose length is related to the position of signal 42; this pulse is effective to position the pick-off in device G<SP>2</SP>. Similarly, the pick-off in device G' is positioned in accordance with the position of signal 43. In Fig. 7, the signal consists of a recurrent group comprising three reference signals O<SP>1</SP> . . . O<SP>3</SP> three variable position signals P<SP>1</SP> ... P<SP>3</SP>, and a group signal A. The group signal is isolated at B and appears as a single pulse for application to a delay line D from which tappings are taken to the grids of valves 53 ... 55. The three reference signals are isolated at S and appear as three single pulses O<SP>1</SP>, O<SP>2</SP>, O<SP>3</SP> applied to valves 53,... 55; as a result each valve 53... 55 becomes conductive in turn as the pulse A<SP>1</SP> on valve 53 coincides with the first single pulse O<SP>1</SP>, the pulse A<SP>2</SP> on valve 54 with the second pulse O<SP>2</SP>, and the pulse A' on valve 55 with the third pulse O<SP>3</SP>. Each of valves 53...55 in turn passes a pulse for application to the delay lines in G<SP>1</SP>, G<SP>2</SP>, G' from which pickoffs pass delayed pulses to devices L<SP>1</SP>, L<SP>2</SP>, L<SP>3</SP> also fed with variable duration pulses 56, 57, 58 produced in W under the control of the three reference signals and the three position signals. Each device L<SP>1</SP>, L<SP>2</SP>, L<SP>3</SP> feeds the appropriate device G<SP>1</SP>, G', G<SP>3</SP> to position the pick-offs in accordance with the position signals. As applied to radar, Fig. 8, pulses 64 are radiated from 60 and echoes are received at 61. The pulses 64 are applied to delay line 5 and to a circuit W where they are combined with pulses P from 61 to produce pulses whose length corresponds to the displacement of the echo from the radiated pulse. These pulses are applied to L where they are compared for coincidence with the pulse from the pick-off 2, the current resulting from coincidence actuating motor M to move the pick-off until the delayed pulse from 5 just fails to coincide with the pulse from W. The position of the pick-off then corresponds to the distance of the echo-producer. If a recording sheet is rotated about the terminal of the delay line 5 in synchronism with the rotation of the devices 60, 61, and the pick-off carries a recording style, a P.P.I. type of record may be obtained. The pick-off may be capacitative or inductive; the moving coil K Fig. 1 may be controlled by a spring or by a steady biasing current; the reference pulse may be applied to the pick-off and the pulses 31 Fig. 1 of variable duration to the delay line 8-10 Fig. 1 may be circular, linear or curved to an arc. Specification 659,007 is referred to.