Assisted-braking resistor to increase rope friction when there is a large weight difference between belayer and lead climber. In the event of a fall, the OHM increases the amount of rope friction so that a lighter belayer can hold a heavier lead climber without difficulty.
Belayer requires significantly less hand braking force to arrest a fall
Lowering a heavier climber is much easier to control
OHM is attached at the first bolt in the safety chain
Should a lead climber fall at the first bolt, the OHM significantly reduces the risk of a possible ground fall
Rope handling when belaying a lead climber not affected (no additional friction when paying out rope)