Deflecting beam:

The dual-signal deflecting beam torque wrench was patented by the Australian Warren and Brown company in 1948. It employs the principle of applying torque to a deflecting beam rather than a coil spring. This helps prolong wrench life, with a greater safety margin on maximum loading and provides more consistent and accurate readings throughout the range of each wrench. The operator can see and hear when a dual-signal wrench reaches the selected torque, since the signal can be seen and heard.