Why aren't older models supported prior to Active2?

The previous model is not a specification for a blood pressure sensor. We require a higher-performance sensor than a sensor from an existing product that only measures heart rate. Because blood pressure is measured using the Pulse Wave Analysis (PWA) method, accurate pulse shape analysis is required. These specifications will be implemented beginning with Active2. 

Electrode sensors are required for ECG measurements, but they are not mounted on previous models."