Among SCR-family devices, which one has two control gates (an anode gate and a cathode gate) and can be triggered from either side depending on configuration?

Introduction / Context:SCR family devices include SCR, SCS, SUS, SBS, and TRIAC/DIAC. Each has distinct gate arrangements and triggering behaviors. The Silicon Controlled Switch (SCS) resembles a thyristor but provides additional control via two separate gates.Given Data / Assumptions:

• Focus on number and placement of gates.
• Standard textbook definitions of SCR-family parts.

Concept / Approach:An SCS includes both an anode gate and a cathode gate. This dual-gate construction allows more flexible triggering and commutation methods versus the single-gate SCR.Step-by-Step Solution:1) SCR: one gate (cathode gate) only.2) SCS: two gates—anode gate and cathode gate—enabling bidirectional control actions.3) SUS/SBS: small-signal triggering devices without the two-gate control of SCS.4) DIAC: a bidirectional trigger device without a gate terminal.Verification / Alternative check:Device symbol references clearly show SCS with two gates; most power electronics handbooks confirm this distinctive feature.Why Other Options Are Wrong:

• SCR: single gate only.
• SUS/SBS: do not have both anode and cathode gates.
• DIAC: trigger diode, no gate terminal.

Common Pitfalls:

• Assuming “bilateral” in SBS implies two gates—bilateral refers to conduction direction, not gate count.
• Confusing TRIAC (two-way thyristor) with SCS; TRIAC also does not have “two gates” like SCS.

Final Answer:SCS (Option B).