What’s the difference between two-circuit and single-circuit track?

You can think of two-circuit track as two tracks combined as one. Two-circuit track enables the use of two separately controlled circuits on one section of track. The two-circuit track can be wired with two separate feeds. Each track circuit can then handle up to 2400 watts (de-rated to 1920 usable watts is recommended). This saves on installation costs by eliminating the need for separate runs. Another option is to use one circuit feed and control it with two switches.