The low-frequency pulsation mode is caused by an imbalance between the emission rate and supply rate of the liquid in Taylor cone volume. This imbalance leads to the contraction of the cone volume during the jetting of the liquid. The liquid could jet after the turn-on of a pulse voltage because of an exertion of electric force on the liquid meniscus, and withdraw before the turnoff of a pulse voltage because of an insufficient supply. In this mode, the ratio of the jetting frequency to the voltage frequency is found to be 1/N, where N is the natural number. Although a jump transition or a sawtooth transition of the jetting frequency was experienced at different flow rates, voltage amplitudes, duty ratios, and voltage frequencies, the experiments proved that the jetting frequency varied as f_volt/N.