We use VTEL’s MCU and NEC BOD terrestrial station equipment when V35 networking. Using H320 and H331 protocol, the voice and digital of vp8020 terminal local loopback is normal, but can’t connect to the MCU of terrestrial station.
1. Local loopback by v35 interface DB25, VP8020 terminal is normal. So our company’s terminal device is ok.
2. Make sure the transmission link is ok for use. After examination, it’s ok.
3. We doubt MCU doesn’t open or has a wrong set. But after examination, it’s ok.
4. Ask the user about satellite transmission link and check the situation of terrestrial station. We find the NEC BOD’s IDU device (indoor unit, it’s a modem for satellite signal) is not online normally. So the transmission link is blocked.
5. Check for the reason, aid the customer technician, and set the data as instructions. There is no problem.
6. After exam carefully, we find that the frequency data of the satellite instructions is wrong. The original frequency has been used by other satellite, so it can’t be online.
7. Change to another frequency, the device comes to normal.
The transmission link is blocked because the frequency data of the satellite terrestrial station is wrong.