Feature of callable convertible bonds that prevents their issuer from calling them for early redemption, no matter how low the market interest rate falls, until the hard call protection period is over or unless the issuer pays a premium specified in the bond indenture. Thus the investor can enjoy the original interest income without the fear that the issuer will call the bond to reissue it at the lower interest rate. This period typically is three years from the date of issue, but also can range anywhere from two to five years. The longer the protection period, the more attractive the bond as an investment.