# 1.2.10 Adjacent channel selectivity (ACS)

The receiver selectivity is often given as Adjacent Channel Selectivity (ACS) – i.e. when the concept of "channel" has been defined for the system being considered. As the wording suggests, this parameter defines the requirement in case one single <span data-highlighted="true" data-vc="highlighted-text"><span class="_kqswh2mm"><span class="_5pioz8co _189e1dm9 _1il9buyh _19lc184f _d0altlke" data-testid="definition-highlighter">ILT</span></span></span> is set at the centre frequency of the (first) adjacent channel. The values for the second and third adjacent channel are occasionally also defined by a standard. However, standards generally implicitly define the interfering signal as of the same system type as the victim, i.e. using the same bandwidth and generally the same or at least a similar modulation scheme.