Symphony® Plus SDe Controllers (SPC) are the next generation of time-tested, field-proven SD series controllers. Specifically designed for the evolution, enhancement, and expansion of Harmony Rack (HR) systems, SDe controllers provide flexible, mounting options that allow them to be installed in multiple configurations. In every form, the controllers are form, fit, and functional replacements for HR controllers. Offering complete scalability, the powerful controllers are suitable for small to large applications.