Explanation: A **TRIAC** (TRIode for Alternating Current) is designed to control AC power. It can be understood as two Silicon Controlled Rectifiers (SCRs) connected in inverse parallel, or "back-to-back," with a single common gate terminal. This unique configuration allows it to conduct current in both directions when triggered by a gate pulse, making it ideal for switching and phase control of AC loads. A **JFET** is a field-effect transistor that controls current flow via a gate voltage and is unrelated to SCRs. A **dual-gate MOSFET** is also a field-effect transistor with two gates for enhanced control, not an SCR-based device. A **DIAC** is a bidirectional trigger diode that breaks down at a specific voltage to conduct in either direction, but it lacks a control gate and is not typically described as two SCRs with a common gate.