with provision for selection from a number of preset intervals

Clocks with attached or built-in means operating any device at preselected times or after preselected time-intervals > Mechanisms measuring a chosen time interval independently of the time of day at which the interval starts > acting only at the end of a single time interval > with provision for selection from a number of preset intervals

Clocks with attached or built-in means operating any device at preselected times or after preselected time-intervals (if restricted to producing acoustic time signals by electrical means G04C21/00) > Mechanisms measuring a chosen time interval independently of the time of day at which interval starts > acting only at the end of a single time interval > with provision for selection from a number of preset intervals