It has been recognized that the adaptive control of EDM can improve its performance and reduce the production costs. Various systems are being attempted in university laboratories in cooperation with EDM manufacturers across Europe, Japan and U. S. A. Although general approach seems to be the same, these systems widely differ in the areas of identification and monitoring the change of gap condition from sparking to arcing. These methods include measuring the voltage at two points during the pulse, measuring the Radio Frequency emission and the stochastic analysis of the gap condition signals. The paper presents a brief survey of the different techniques of detection and AC systems for EDM.