Match the control/measurement elements with their roles: (A) Synchro, (B) Amplidyne, (C) Servo, (D) RC network — with (1) Amplifier, (2) Actuator, (3) Compensator, (4) Transducer.

Introduction:
Classical control systems use sensing, actuation, amplification, and compensation blocks. Recognizing each device’s role is key to reading block diagrams and designing stable loops.

Given Data / Assumptions:

• Synchro — electromechanical angular sensor.
• Amplidyne — high-gain electromechanical amplifier.
• Servo — actuator for precise position/velocity control.
• RC network — analog compensator (lead/lag).

Concept / Approach:

A synchro converts shaft angle to electrical signals, i.e., a transducer. An amplidyne is a controlled DC generator delivering amplified power, hence an amplifier. A servo mechanism (servo motor + control) produces motion/force, serving as an actuator. RC networks shape loop frequency response to improve stability and performance, i.e., compensators.

Step-by-Step Solution:

Verification / Alternative check:

Standard control texts classify sensors (transducers), actuators, amplifiers, and compensators similarly; Bode plots of RC networks exhibit lead/lag shaping.

Why Other Options Are Wrong:

Swapping roles misrepresents device physics: e.g., a synchro does not amplify; a servo is not a compensator; an RC network does not act as a power actuator.

Common Pitfalls:

Confusing servo controller electronics with the actuator itself; assuming any sensor is an actuator.

Final Answer:

A-4, B-1, C-2, D-3