Single-phase generator The early generators for those single-phase traction networks are single-phase generators. Even with newer three-phase motors which were introduced to some modern trains, the single-phases transmission for traction networks survive their time and are still in use in many railways today. However, many traction power stations have replaced their generators over time to use three-phase generators and convert into single-phase for transmission. In the early development of hydroelectricity, single-phase generators played an important role in demonstrating the benefits of alternating current. In 1891, a 3,000 volts and 133 Hz single-phase generator of 100 horsepower was installed at Ames Hydroelectric Generating
Single (music) released as a single may not appear on an album. As digital downloading and audio streaming have become more prevalent, it is often possible for every track on an album to also be available separately. Nevertheless, the concept of a single for an album has been retained as an identification of a more heavily promoted or more popular song (or group of songs) within an album collection. Despite being referred to as a single, singles can include up to as many as three tracks. The biggest digital music distributor, iTunes Store, accepts as many as three tracks less than ten