[en] In 12 GeV proton synchrotron in the High Energy Accelerator Research Organization, proton beam incident into main ring with 500 MeV of energy in accelerated to 12 GeV to lead to a physical laboratory after pulling out from the ring. At a process of acceleration in the main ring, a phenomenon shifting stable acceleration region of RF phase against beam occurs. The region occurring this phenomenon is called phase transition region. When passing through this region, proton beam loses beam with high density, especially affects a definite effect to its accelerating efficiency. As a method of preventing this effect, a method to shorten the time passing through near the transition region as possible is well known. This can be carried out by using a tetrapole electromagnet mounted in the ring. For this purpose, two sets of pulse waveform forming source to pulse excite a tetrapole electromagnet mounted at the main ring and a control board to intend for cooperative operation of these two sets of sources were developed, by using which some experimental results satisfying various conditions were obtained