自从出现半导体器件以后,收信-放大电子管发展的速度并没有减低。相反的,在最近十年间这类电子管的型号的数量很快地增加了。同时随着它们在结构上的革新,质量上也有了一系列的重大改进。根据电子管产品的统计,在1949年生产的共有15000种收信-放大管, Since the emergence of semiconductor devices, the letter - enlarge the speed of the tube did not reduce. In contrast, the number of models of these tubes has rapidly increased in the last decade. At the same time as they are structurally innovative, there are a series of significant improvements in quality. According to the statistics of the tube products, a total of 15,000 kinds of receiving-amplifying tubes were produced in 1949,