GB593461A - Electric pulse generating system - Google Patents

Abstract

593,461. Impulse generators. STANDARD TELEPHONES & CABLES, Ltd. Feb. 25, 1944, No. 3576. Convention date, Feb. 27, 1943. [Class 40 (v)] In a pulse generator, a gas-filled valve is fired to develop a pulse in the cathode circuit, the pulse effecting the build-up of a potential controlling means for shunting the cathode circuit to define the trailing edge of the pulse. Gas-filled triode 10, fired by a triggering pulse when the A.C. fed over lead 20 is near its peak value, forms the leading edge 41 of a positive pulse on the cathode of valve 10. Condenser C2 charges over resistance R3, reducing the bias on gas-filled triode 12 until valve 12 fires, shunting the upper part of potentiometer R2 and defining the trailing edge 53 of the pulse. The fall in the A.C. voltage on lead 20 extinguishes valves 10, 12, condenser C2 discharging through the grid path of valve 12 acting as a hard diode. The duration of the pulse is determined by the time-constant circuit R3, C2 and the setting of potentiometer R2. Valve 10 may be biassed so that it fires at a point on the positive half-wave or D.C. may be used, the valves being extinguished by a negative impulse or the opening of the anode circuit of valve 10. Condenser C1 controls the shape of the leading edge 41 and may give an extension 76. As applied to a radar system, Fig. 3 (not shown), the modulator pulse triggers the device, edge 41 being coincident with the commencement of the time base trace. Adjustment of potentiometer R2 causing edge 53 to become coincident with the trailing edge of an echo, enables the range to be read from a calibrated dial. A phase-shifting device may be included in the lead 20 to ensure valve 10 triggering at the correct point in the A.C. mains cycle. Specification 593,467 is referred to.