A chiropractic adjusting instrument comprising: - an impact head, - a housing having an opening and containing - an electromechanical drive mechanism having a preload activation position and coupled to the impact head and having - a thrust nose piece movably mounted in the housing and comprising a preload end and an outer end including an outer end shank for coupling to at least one impact head, the outer end shank extending through the opening, - a preload switch plunger coupled to the preload end of the thrust nose piece, - a solenoid mounted in the housing and comprising: a longitudinal axis and a core having a third passage to accept the preload switch plunger so that the core is movable along the longitudinal axis and is in alignment with the thrust nose piece, - a preload spring interposed between the preload side of the thrust nose piece and a second inner housing stop having a second passage to accept the coupled preload switch plunger preload end, - an electronic pulse system coupled to an electric power source and the electromechanical drive mechanism, and - a triggering system comprising a switch by which the triggering system coupled to the electromechanical drive mechanism and characterized by - the triggering system coupled to the electromechanical drive mechanism by a trigger switch which can not activate the electronic pulse system to energize the electromechanical drive mechanism unless the preload switch plunger extends to the switch and activates the switch when the thrust nose piece has compressed the preload spring to the preload switch plunger preload end. - an impact head, - a housing having an opening and containing - an electromechanical drive mechanism having a preload activation position and coupled to the impact head and having - a thrust nose piece movably mounted in the housing and comprising a preload end and an outer end including an outer end shank for coupling to at least one impact head, the outer end shank extending through the opening, - a preload switch plunger coupled to the preload end of the thrust nose piece, - a solenoid mounted in the housing and comprising: a longitudinal axis and a core having a third passage to accept the preload switch plunger so that the core is movable along the longitudinal axis and is in alignment with the thrust nose piece, - a preload spring interposed between the preload side of the thrust nose piece and a second inner housing stop having a second passage to accept the coupled preload switch plunger preload end, - an electromechanical drive mechanism having a preload activation position and coupled to the impact head and having - a thrust nose piece movably mounted in the housing and comprising a preload end and an outer end including an outer end shank for coupling to at least one impact head, the outer end shank extending through the opening, - a preload switch plunger coupled to the preload end of the thrust nose piece, - a solenoid mounted in the housing and comprising: a longitudinal axis and a core having a third passage to accept the preload switch plunger so that the core is movable along the longitudinal axis and is in alignment with the thrust nose piece, - a preload spring interposed between the preload side of the thrust nose piece and a second inner housing stop having a second passage to accept the coupled preload switch plunger preload end, - a thrust nose piece movably mounted in the housing and comprising a preload end and an outer end including an outer end shank for coupling to at least one impact head, the outer end shank extending through the opening, - a preload switch plunger coupled to the preload end of the thrust nose piece, - a solenoid mounted in the housing and comprising: a longitudinal axis and a core having a third passage to accept the preload switch plunger so that the core is movable along the longitudinal axis and is in alignment with the thrust nose piece, - a preload spring interposed between the preload side of the thrust nose piece and a second inner housing stop having a second passage to accept the coupled preload switch plunger preload end, - an electronic pulse system coupled to an electric power source and the electromechanical drive mechanism, and - a triggering system comprising a switch by which the triggering system coupled to the electromechanical drive mechanism and characterized by - the triggering system coupled to the electromechanical drive mechanism by a trigger switch which can not activate the electronic pulse system to energize the electromechanical drive mechanism unless the preload switch plunger extends to the switch and activates the switch when the thrust nose piece has compressed the preload spring to the preload switch plunger preload end.