这其中有些标准设定了必须保留测试结果的时间长度。
Some of these standards have a set amount of time that you must retain test results.
该系统采用8031单片机进行控制，根据控制命令可发出不同时间间隔、不同时间长度、不同频率的标准正弦波信号。
The system is controlled by chip microprocessor 8031 and can transmit standard sinusoidal waves with various frequencies and arbitrary time intervals according to various requirements.
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