Existing mutual fund schemes will not require approval of a majority of unit holders to invest in derivatives segment provided the investors are given the exit option, Sebi said today.Among other conditions, the relaxation, effective immediately, would be in place only if the mutual fund scheme concerned provides the investors 30 days time to exit the scheme without any charges.It would be applicable for existing mutual funds, whose Scheme Information Documents (SIDs) do not envisage investments in derivatives.