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图1所示的设计是一条看得见的光链路,可供需要观看被传送的数据的人使用。该设计的一个附加优点是隔离电平高达5000V以上。对该系统的测试使用了数据采集系统的COM输入端以及标准PC的COM端口。MC1489将RS-232C的数据变换成TTL信号,7404门电路再将TTL信号倒相。7404的输出信号驱动Q1,即2N3055型功率晶体管。该功率晶体管驱动3只发光二极管(LED),以组成一个光源。
The design shown in Figure 1 is an optical link that is visible to anyone who needs to view the data being transmitted. An added benefit of this design is isolation levels up to 5000V or more. The system was tested using the COM input of the data acquisition system and the COM port of a standard PC. The MC1489 converts the data of the RS-232C into a TTL signal, and the 7404 gate inverts the TTL signal. The output of the 7404 drives Q1, the 2N3055 power transistor. The power transistor drives three light-emitting diodes (LEDs) to form a light source.