The object of the present invention is to provide a dispersion stabilizer that can minimize coagulated precipitation of a protein under acidic conditions, especially in the pH range of around pH 5 which is closer to neutrality than the range around the isoelectric point of the protein. Thus, a handoff of a voice call involving the AT may be initiated from the circuit services network to the packet data networking prior to the AT establishing a call dialogue with the packet data network. The filter unit is used for the filtrating the reaction solution and fixed by screws to a bottom of the cartridge main body. The processor can additionally compensate for propagation delays by adjusting switching times.