How Symphonie creates 2.5 V and 5 V excitation while being run from only 1.5 V D-Cell batteries

The Symphonie system uses DC to DC power supply (converter) technology to boost the 1.5 V D-Cell battery voltage up to 5 V and 2.5 V.

The choice for using D-Cells is the significantly larger battery capacity (Amp-hour rating) when compared against 9 V transistor batteries.

DC to DC power supplies coupled with D-Cells are more efficient than using traditional voltage regulators and 9 V batteries.