A hand held injector (20) for injecting fluids from a syringe into an animal subject including: a power head (22) including: an injector housing (47)； a bidirectionally movable drive piston (46) in a first piston direction and a second piston direction along a longitudinal axis of said actuation piston, said first piston direction corresponding to a fluid discharge direction； a motor coupled with drive to said drive piston to selectively advance and remove said drive piston along said longitudinal axis； a plurality of buttons (90) used for the control operation of said power head； and a trigger (36) mounted on a pivot (110) of said injector housing, said trigger being movable so that it moves in first and second trigger directions； wherein the thrust in a front portion of said trigger in said first trigger direction generates a control signal for said motor such that said drive piston travels along said longitudinal axis in said first piston direction, where the pushing in a rear portion of said trigger in said second trigger direction generates another control signal for said motor such that said drive piston travels along said longitudinal axis in said second piston direction, characterized in that. said trigger has a series of magnets associated with it, wherein said injector further includes a trigger control signal sensor (116), said sensor being adapted to detect a magnet of said series of magnets, and wherein said trigger control signals they are supplied wirelessly from said trigger to said motor by means of a magnet.Un inyector de sujeción con la mano (20) para inyectar fluidos desde una jeringa a un sujeto animal incluyendo: un cabezal de potencia (22) incluyendo: un alojamiento de inyector (47)； un pistón de accionamiento (46) bidireccionalmente móvil en una primera dirección de pistón y una segunda dirección de pistón a lo largo de un eje longitudinal de dicho pistón de accionamiento, correspondiendo dicha primera dirección de pistón con una dirección de
