This ticker tape timer has everything you need in one box including a wall plug adapter so no power supply is needed. This timer is the time tested way for students to visualize distance, velocity, and acceleration versus time. For example, hook this to an inclined car on a ramp and you will get a visualization of acceleration caused by gravity, seen by the spacing between spots on the tape. A vibrating striker prints dots on the tape using carbon discs at a selectable rate of 25 or 40 dots per second (dependent on your selection). The unit is housed in a durable, scratch proof and shock absorbing plastic case with a unique method of adjusting the position of the carbon disc. Extra Paper Tape Roll - PH0353B. Comes with 100 Carbon Discs and one 50m roll of tape. Operates on 12 volts (adapter included).