Abstract: An improved arming and firing device especially suited for rocket motors. An explosive donor charge is packed against a bulkhead formed in the body of the device. Shock energy generated by the donor charge and transmitted through the unruptured bulkhead sets off a shock-responsive receptor charge, which in turn initiates a pyrotechnic or explosive rocket motor-actuating output charge. The bulkhead prevents blow-by or leakage of the rocket's combustion products. The donor charge is ignited by an electrically activated detonator. The detonator is carried by a moveable holder. The holder is moved against a return spring by electromechanical driving means. Arming the device is accomplished by moving the holder to position the detonator in firing train with the donor charge, thereby simultaneously bringing electrical contacts on the detonator into contact with electrical leads on a switch plate located adjacent the holder and thus closing the firing circuit.