The CT 100 O and CT 100 C are used as optical or contact revolution counters. The measuring range of the CT 100 O is from 60 to 60,000 rpm while the CT 100 C is from 30 to 20,000 rpm.
The CT 100 O has an optical probe, transport case and calibration certificate. And the CT 100 C also has an optical probe, transport case, calibration certificate and ETC adapter.