When on duty, employees will devote their entire time and energies to the duties and responsibilities of their assignment.  While a high level of performance or a continuous effort towards improved and increased performance should be the goal of every employee, a standard level of reasonable quality performance (as judged by previous experience or by the activity of other employees performing similar duties) will be considered minimum acceptable performance.  Sustained performance below this minimum level, which cannot be satisfactorily explained, will be grounds for disciplinary action.