672,015. Phase difference measurements. UNION GENERALE BELGE D'ELECTRICITE SOC. ANON. Jan. 2, 1950 [Dec. 31, 1948], No. 77/50. Class 37. In order to measure the phase difference between two alternating voltages, a positive voltage pulse produced by one voltage at one of its passages through zero in each cycle is applied to the grid of a gas discharge tube so as to trigger the discharge and a negative voltage pulse produced from the other voltage at one of its passages through zero in each cycle is applied to the anode to extinguish the discharge, the mean anode current then being proportional to. the phase difference. One of the voltages is applied across conductors 24, Fig. 2, and the other across terminals 50. The conductors 24 are connected across the primary winding 26 of a transformer 27, the secondary winding 28 of which is connected in series with a resistance 29 in the grid circuit of a triode 30. The anode 31 of this valve is supplied through a resistance 35 from a source divided into two parts 171, 17<SP>11</SP> in series. Pulses are produced by means of a condenser 37 and high resistance 38 and are applied to the grid 43 of a cathode follower valve 39 having a comparatively low resistance 40 in its cathode circuit. The potential across the resistance 40 is applied through a condenser 44 to two resistances 45, 46 in series with the cathode 47 of a thyratron 9, so that these resistances are m the anode circuit of the thyratron in series with an ammeter 21. When a positive voltage pulse is applied to the resistance 40 a current flows through the resistances 45, 46 in the direction of the arrow X and decreases the voltage applied to the anode 25 which extinguishes the discharge if this has already been triggered by the application of a positive pulse to the grid 49. The conductors 50 are connected to the primary winding 51 of a transformer 52 of which the secondary winding 53 is in series with a resistance 54 in the grid circuit of a triode 55. This produces pulses by means of a condenser 60 and resistance 61 which pulses are applied to the grid 66 of a cathode follower 62 having a resistance 63 in its cathode circuit. When the grid 66 is subjected to voltage pulses a condenser 67 allows a current to pass, which produces variations of potential at the terminals of resistances 68, 69 in series with the grid 49, thereby applying to the grid 49 a positive voltage pulse superposed on the constant negative bias from the source 8 and triggering the discharge. A recording ammeter 22 may be substituted for the resistance 45 by a changeover switch 23. In a modification, Fig. 3, the variations of voltage across the resistance 40 are injected into the anode circuit of the thyratron 9 by means of current pulses flowing in a resistance 45<SP>1</SP> between the anode 25 and the source of constant voltage 171. The ammeter 21 may be connected across the resistance 45<SP>1</SP>. In another modification, Fig. 4, the voltage pulses are applied to the anode of the thyratron 9 by means of a transformer 72 the secondary winding 73 of which is connected through condensers 44, 74, across a resistance 75 corresponding to the resistances 45, 46, Fig. 2. In the arrangement shown in Fig. 5, the voltage pulses applied to the anode 42 are produced across a resistance 76 connected between the source 171, 17<SP>11</SP> and the anode 42. These pulses are injected into the anode circuit of the thyratron 9 through condensers 77, 78, either to the terminals of a resistance 46, as shown in full lines, or of a resistance 45<SP>1</SP>, as shown in broken lines. In a further alternative, Fig. 6, the negative pulses are applied between the cathode 47 and anode 25 by means of a transformer 79.