The ST-PA2 features a single, unbalanced audio input, a gain control, and two outputs. The first output is designed to deliver a clean 2 watts RMS into an 8 ? speaker. The second output is intended to drive 600 ? transformers, typically on equipment inputs. This makes the ST-PA2 uniquely suited to applications such as music-on-hold inputs on telephone systems which may have either 8 ? or 600 ? inputs. If desired, both outputs may be used at the same time.