Abstract: A test instrument for generating controlled bursts of electrical noise for use in testing the response of electronic equipment to such noise. A high voltage induction coil has its primary winding connected in circuit with a semiconductor switching means across a source of DC potential whereby when the current flow through the primary winding is interrupted, a relatively high voltage is developed across spark electrodes connected in the secondary winding of the coil and a spark discharge results. The spark discharge is, of course, rich in high frequency noise components which radiate therefrom to the system under test. The test instrument includes controls for causing the spark discharge to be generated either when triggered by a signal from the system under test, or by the manual operation of a push button switch, or at rates which may be varied by the operator.