| 摘要 |
There is disclosed a method and an apparatus for alternately effecting the actuation and non-actuation of a responsive instrumentality in a manner such that during actuation of the instrumentality, cooperation can be effected for a variable system condition. The apparatus comprises a first timer having a timing period and a non-timing period, a second timer connected to the first timer also having a timing period and a non-timing period wherein the first timer is adapted to switch to the non-timing period after the timing period is completed and upon switching to the non-timing period actuates the second timer into its timing period. The second timer is connected to the instrumentality to be actuated and the instrumentality is actuated whenever the second timer is in its timing period and is not actuated when the second timer is in its non-timing period. Sensing means are connected to the second timer for continuously sensing a predetermined system condition and wherein the duration of the timing period of the second timer is responsive to the sensing means. Control means are connected in circuit with the instrumentality to be actuated as well as to the first and second timer wherein the control means is adapted to initially place the first timer to its timing period and the second timer into its non-timing period wherein after the timing period of the first timer is completed, the first timer switches to its non-timing period thereby placing the second timer into its timing period and thereby causing the instrumentality to be actuated, this actuation continuing until the second timer switches into its non-timing period whereby the first timer again switches to its timing period thereby effecting the alternate actuation and non-actuation of the instrumentality.
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