Illustration of the behaviour of the CARMENES visible channel CRX for the mid-M dwarf EV Lac. Top-left: variation of RV as a function of wavelength (spacing is logarithmic). The CRX-index is the slope of RV vs log(λ) for each spectrum. A total of 10 CARMENES spectra are shown covering approximately one stellar rotation. The upper and lower boundaries are the fits to the most positive and negative RV values. Top right: The CRX-gradient, illustrating the CRX-index as a function of the ‘mean’ RV. Bottom-left and bottom-right: CRX vs. rotation phase and RV vs rotation phase illustrating the anti-correlation of CRX-index (i.e. the negative CRX-gradient shown in the top right panel). The plotted points in each panel are colour coded according to stellar rotation phase.