Two stages in the relaxation process for conical‐helical perturbation in cholesteric liquid crystals are seen when a dc electric field is applied. The second stage, which is accompanied by the growth of optical rotation with time, is relatively long. By replacing the dc field with a 30‐ to 60‐Hz ac field, this long relaxation stage can be eliminated and the total relaxation time is shortened. However, this also causes the response time to become longer, as compared to the response to a dc field. A four‐electrode cell and an ac‐dc combined technique is described by which both advantages of rapid response and relaxation times are achieved.