Patent GB-1051157-A (GB)
IPC: G01R31/11
Abstract: 1,051,157. Pulse echo testing of electric lines. SIEMENS & HALSKE A.G. Sept. 26, 1963 [Sept. 28, 1962], No. 38045/63. Heading H4D. In pulse testing of electric lines distortion in the echo pulses resulting from the characteristics of the line, is corrected by means (Fig. 2) comprising an amplifier having two parallel channels, the first channel I having an amplification vers. frequency relationship corresponding to the attenuation vers. frequency relationship of a predetermined length of line, and the second channel II having a fixed amplification equal to the low frequency amplification of the first channel and a delay equal to the average delay of the first channel, wherein the outputs of the two channels are fed to a combined output in relative amounts determined by a control quantity so varied in time, in dependence on the length of line being instantaneously scanned, that the combined output produces an undistorted echo-pulse irrespective of its point of origin along the line. The invention is described as applied to the pulse testing equipment described in Specification 974,060, and shown in Fig. 1 (not shown), the normal single channel correction circuit 6 being replaced by the two-channel amplifier means of the invention. In the arrangement of Fig. 2 the outputs of the two channels are applied across a potentiometer 22 having a wiper connected to the output terminal E1 and controlled in position by the ramp output of generator 14 via control arrangement 23 such that when the nearest portion of the line is being scanned the wiper is near terminal 28, taking output from channel II only, with minimum correction and when the far end of the predetermined length of line is being scanned the wiper is near terminal 27, taking output from channel I only, with maximum correction. As an alternative to potentiometer 22, terminals 27 and 28 may be respectively connected to the control grids of two cathode coupled variable-Á valves 24 and 25, Fig. 3 (not shown), with a common cathode load resistor 26. The ramp output of generator 14 is fed to arrangement 23 which produces the voltages shown for application to the control grids of the two valves. The application of the said voltages to the grids changes the amplification of the two valves in opposite directions such that at output terminal 33 a signal appears having relative amounts of the outputs from the two channels varying with time as required. Since the display in Fig. 1 is expanded and divided into equal increments of line length, correction of the echo pulse over the complete length of line cannot be accomplished by the first channel amplifier 20 alone, which amplifier only provides incremental correction of the said incremental line length. Preliminary correction stages 34, 35 and 36 are provided therefore, providing individual additional corrections, when the respective CR circuits 43, 44 and 45 are switched in, equal to that of amplifier 20. The CR circuits are switched in under the control of the output of generator 15, Fig. 1. in synchronization with the vertical C.R.T. deflecting steps produced by means 17. Stages 34, 35 and 36 together with their CR circuits may be comprised, as shown in Fig. 4 (not shown) of a triode amplifier stage having a CR ladder circuit switchable into its cathode circuit.