Under power-based capture, a transmission is correctly decoded at the destination, even in the presence of other transmissions, if the received signal-to-interference-plus-noise ratio (SINR) exceeds a threshold b ges 0. Studies on capture are often limited to the case b ges 1. In this paper, we study capture for systems with arbitrary b ges 0, i.e., our formulation includes both wide-band (0 les 1) and narrow-band (b > 1) systems. We also point out some ambiguity from the existing literature on capture analysis