<p>This paper focuses on the output feedback event-triggered control problem for high-order fully actuated systems (HOFASs). Unlike existing results, two event-triggered mechanisms are employed for the output and estimated states, respectively, whose trigger thresholds are time-varying functions. First, only based on the triggered output, a novel state observer is constructed to estimate unmeasurable states. Second, for the estimated states, an event-triggered mechanism is proposed to reduce their update frequency. Then, an event-triggered controller is established with the help of the fully actuated system method, which only utilizes the triggered estimated states, and avoids the introduction of virtual controllers. By the use of Lyapunov stability theory, it is strictly proven that all signals of closed-loop systems converge to adjustable boundaries. Finally, the simulation on an RLC circuit serves as a practical illustration to verify the reliability of the proposed control algorithm.</p>