This 2 speed ticket timer is a modern version of tried and tested method of measuring velocity and acceleration. A vibrating striker prints dots on the tape using carbon discs. The unit is housed in hard wearing, inert scratch proof and shock absorbing plastic case and has a single aluminum plate for clamping to the bench or fixing to a dynamics track. It has a unique method of adjusting the position of the carbon disc. 2 speeds 25/s or 45/s This kit is prefect for already established labs / class rooms with 12 volt DC power source. 12 V Power supply is NOT included with this kit. Included with in this kit: Timer tape ( PH0353B) or Carbon discs ( PH0353C).