Observed J = 1–0 and 2–1 lines of CS and its isotopologues ¹³CS, C³⁴S, C³³S, and ¹³C³⁴S toward TMC-1. For C³⁶S and ¹³C³³S, only the J=1–0 line was detected. The abscissa corresponds to the local standard of rest velocity of the lines adopting the rest frequencies given in Table B.1. In the two bottom panel, however, the abscissa corresponds to the rest frequency. The ordinate corresponds to the antenna temperature corrected for atmospheric and telescope losses in mK. The derived line parameters for the observed lines are given in Table B.1. The synthetic spectra (red line) are derived for the column densities shown in Table 1 and the LVG model described in Sections 3 and 4.1. For CS, a two-layer component model is used (see Section 4.1). Negative features appearing in the folding of the frequency switching data are blanked in all the figures. The observed spectrum of the hyperfine component J=1–0, F=1/2–3/2 of C³³S was multiplied by 0.1.