信号站
1.In the earliest experiments guns were fired to produce the sound and also a flash, which at night acted as a signal to show that the experiments had started. An observer standing, say, 20 miles away started his stop-watch when he saw the flash, and stopped it when he heard the explosion.
4.Based on multi-station GPS multi-link signals monitoring,these features are found that the ionospheric irregularities occur most often within the region of 105°~120°E and the south of 27°N,and the irregularities to the north of 23°N decay easily and disappear firstly,but those in the region of 20°~23°N can have a longer duration.
9.Service where the data communication channel is able to transmit signals, but is not equipped to receive signals.
10.17minutes after launching, its first radio signals beeped to the tracking station in Manchester England.
