Listening to the Baltic States' Grid Switch with an Audio Cable

Over the weekend of February 8th, 2025, the Baltic states' electricity grid switched from the Russian grid to the continental European grid. The author, inspired by a curious idea, used a PC's audio input and a simple audio cable as a makeshift sensor. By employing an FFT algorithm to analyze the 50Hz frequency component in the audio signal, they successfully monitored the grid synchronization process. Despite the unconventional approach, the results were surprisingly accurate, closely matching professional monitoring data, demonstrating a creative solution to a unique problem.