A component of an electromechanical step-by-step (SxS) or panel switch, or electromagnetic crossbar (Xbar) circuit switch, that identifies lines that go off-hook to request service. A line finder allows many lines (e.g., 100 or so) to share a bank (10 or so) of selectors, depending on the activity levels of the individual subscribers. See also line, off-hook, panel switch, selector, SxS, and Xbar.