The term 'At Fixed Intervals' refers to a regular pattern of events or activities that occur at specific times. The crossword solutions for this term are 'PERIODIC' (8 letters), 'OCTAVES' (7 letters), and 'SPACED' (6 letters). 'PERIODIC' means occurring at regular intervals, while 'OCTAVES' is a musical term referring to the interval between one note and another eight notes higher or lower. Finally, 'SPACED' means arranged at intervals. All three words refer to the idea of something happening at fixed intervals.