The Digital Signal Rocker™ Switch Take a closer look at those markings on the switch. You can see that there are four functions: Low speed : press the upper section Medium speed: Press the lower section Off: press the upper section twice High: press the lower section twice The switch can actually be programmed for any number of functions... it's just that more than four might get too complex for the user. However, you can program any of those functions to be momentary or latching in either position... Single Pole or Double Pole Push On, Push Off Variable Momentary Stepped There's another plus with the version that has pilot lights: A pilot light in a conventional switch indicates that power is On to the target load. The DS Rocker pilot light indicates whether the load is actually running... or if a fault situation exists. That's because a DSRocker in a digital databus 'polls' the load every few milliseconds. And in addition the pilot light(s) can be programmed to be dependent or independent illumination. Added to all this, the DSRocker switch is ultra-reliable, withstanding over one milliion On-Off cycles. PDF Data Sheets: Heavy Vehicles Marine