A standard optical emitter/phototransistor pair has DC drive current and variable distance sensing up to 1 M. Designated the OPB100, the optical sensor pair is designed to enable circuit designers to specify an emitter/phototransistor sensor with the capability to operate at a custom distance for the cost of a standard sensor. The OPB100 sensor pair is suitable for applications requiring a special slotted switch where standard spacing cannot be used, or for long distance sensing.