Period-K_s-diagram of NGC 147 (upper panel) and NGC 185 (lower panel). C-type LPVs are plotted as black circles, M/S-type LPVs as red squares and unclassified variable red giant stars as blue triangles. The sizes of the plot symbols are scaled corresponding to the photometric amplitudes A_σ (see legend). For LPVs with two detected periods, open symbols indicate the second, longer period of both. The black dotted lines (C′, C, D) mark the PLRs found for the LMC by Ita et al. (2004). They were adopted and shifted according to the distance moduli differences between the LMC and our galaxies (see text). The black thick dashed line shows the PLRs derived by using the LPVs identified in this work. The black thin dashed line in the lower panel is plotted for demonstration purpose only (see text).