—This work presents the analysis and functionalcharacterization of a multi-tap AC voltage stabilizer implemented in LTspice, emphasizing its control, feedback, and protection mechanisms. The stabilizer employs an autotransformer with discrete tap selection, where relay-driven switching provides coarse regulation across varying mains conditions. A dedicated sensing network, consisting of a transformer secondary, rectifier, and precision divider, generates a DC feedback signalproportional to the output RMS voltage. This signal is processed by a window-comparator architecture built around the LM324,enabling the controller to determine whether the present tap is too high, too low, or within the acceptable regulation band. The design incorporates a soft-start and pre-regulation stage that ensures stable startup behavior by delaying relay activation until the reference, supply rail, and sensing nodes reach steady-state values. Comparator thresholds are derived analytically by mapping mains voltage through the transformer ratio, rectifier, and divider network to the LM324 input domain. This allows direct calculation of the window center and allowable mains range for each tap. A protection comparator monitors long-term deviationsoutside the window and, through a zener-coupled reference node, triggers a controlled shutdown or tap change when necessary. The resulting system combines discrete tap switching with analog decision logic to achieve robust voltage regulation across a wide input range, while maintaining predictable and mathematicallyverifiable operating boundaries.