Tel-Tac 2 Eletronic Tach - TELTAC2 Self-contained digital tach with built-in memory. Small, easy to mount. Memory display lasts 30 minutes after car is shut off. Powered by 9 volt battery. 31⁄8 x 31⁄8 dimensions. Works on 4-6-8 cylinder mags or distributors. Max. RPM reading: V8 up to 12,000 rpm 4 and 6 cylinder up to 15,000 rpm. Tel Tac Oval Track Pro shows the highest overall RPM, the four lowest RPM's and the four highest RPM's from 2 laps. This allows you to tune your car correctly, not guess.