By barring a cell, the operator can prevent commercial users from camping on that cell. Certain TEMS Investigation devices, however, have the ability to ignore the access restriction and use the cell anyway. Tests can then be conducted in a controlled environment without interruptions (using an "Only barred" or "Only reserved" option, as exhibited in section "Cell Barred"). This increases the reliability of tests and promotes testing efficiency, as alternative methods can be costly and error-prone. Furthermore, the testing can be done with minimum impact on paying subscribers.