The mechanical endstop uses a lever switch to detect when it is activated. The switch is wired up so that when activated, it pulls the signal to LOW. There is also an LED on the board that will light up when the switch is activated.It uses a standard 4 pin .100" pitch header and accepts a standard, old-style CD-ROM audio connector cable.
1 x Mechanical Endstop Switch Module
compare with optical endstop here.