The Triggers use Linear Hall Sensors now, U10 (RT) and U11 (LT). They have 3 pins, 1 - VDD (power), 2 - Output, 3 - VSS (ground). The VDD for them comes from U9, which is turned on/off by U1 at 125Hz, 8ms period, On ~1.4ms, Off ~6.6ms (~18% Duty Cycle). This is done mainly to save power.