Apparatus and system

An apparatus comprises a plurality of pixels each including a conversion element and a switch, a driving circuit configured to control the switches via drive lines, a bias power supply unit configured to supply a bias potential to the conversion element via a bias line, column signal lines to which signals are output from the plurality of pixels, and a detection unit. The plurality of pixels include a first pixel and a second pixel, which are adjacent to each other in the row direction and are connected to a common column signal line. The switch of the first pixel and the switch of the second pixel are connected to drive lines different from each other. The detection unit determines presence/absence of radiation irradiation based on a current flowing to the bias line.