In a gate drive circuit including stages which are cascaded and which output gate signals each of the stages includes a first node, an output part, a first holding part and a second holding part. and air pressure ranging between 10-1500 psig for a period of 0. The second mechanism, which triggers on overburdening exposure to water, sand, or soil, triggers the relatively longer time-delay fuse. A breech plug body is removably attachable to the breech end of the barrel. Furthermore, based on the output signal, a binary signal representing the presence or absence of electrical connection of the electrode units is output.