Electronic stop watch

摘要

An electronic stopwatch including a time signal generator for generating a repetitive time signal, and a primary counting circuit for counting the time signal and for developing a count representing time in a timekeeping mode of operation. A secondary counting circuit receives the repetitive time signal during an interval to be measured, and develops a count representative of the length of the interval of time during which the time signal was applied thereto. The secondary counting circuit operates in a stopwatch mode of operation. A display selectively displays a time represented by the count of the primary counting circuit or the count of the secondary counting circuit in order to display either present time or a time interval measured in the stopwatch mode. An alarm is connected to receive the repetitive time signal applied to the secondary counting circuit and generates an alarm signal after the repetitive time signal has been applied thereto for a predetermined period of time. Therefore, in the stop watch mode an audible alarm indicates when an interval of time of a predetermined length has occurred and does not require a user of the stopwatch to visually watch the display in order to know when that predetermined interval of time has elapsed.