The ETV diagrams of V505 Lac constructed using Equation (1). The black and gray dots indicate the primary and secondary times of minimum light, respectively, and the filled and open red stars represent the primary and secondary timings measured at the SOAO, respectively. In panel (a), the black dashed line corresponds to Equation (2). Enlarged ETV diagrams (b) and (c) show the TESS timings obtained during Sector 16 and Sectors 56 and 57, respectively.