In fact, when a network failure occurs, a preliminary judgment can be made from the MODEM indicator. On the MODEM panel, there are mainly carrier signal indicator CD (109 signal), reception signal indicator RD (104 signal), and transmission signal indicator SD (103 signal).
The CD indicator light represents a carrier detection signal. The light is on, which means that the MODEM receives the carrier signal from the line, and the carrier signal level received from the line has entered the specified range. When the RD and SD indicator lights are on, it means that the MODEM and the terminal have data signals on the leads 103 and 104, the RD light is on, which means that the data is received, and the SD light is on, which means that the data is sent.
When the network is working normally, the carrier signal indicator CD is brighter and does not flash. The send signal indicator SD and the received signal indicator RD are similar, but the brightness is slightly worse than the carrier signal indicator lamp and flashes.
When a network failure occurs, you can initially judge the network failure based on the indicator lights on the panel.
(1). The carrier signal indicator CD is not lit or the brightness is much darker than normal, and it flashes frequently, which may cause the line to be blocked or the signal quality is too poor.
(2). The received signal indicator light RD is not on, and the carrier signal indicator light CD does not change significantly. The network node machine may be faulty.
(3). The receiving signal indicator light RD is much darker than normal and the flash time interval is significantly extended, so the line level may be too low.
(4). The received signal indicator light RD is much brighter than normal, and the flash time interval is significantly shortened, so the line level may be too high.
(5). If the sending signal light SD is not on, the fault may occur in the local URL or terminal.