VP8020 terminal connect in 3*BRI by ISDN relay.
1,In the main conference site there are two 8020 terminal connect each other, the image is well, we see the CRC is 0 from 8020 operation bench.
2,When the two 8020 terminal make a conference by MCU, the image is well, we see the CRC is 0 from 8020 operation bench.
3,Test the point to point view between the branch sites, we see the CRC is 0 from 8020 operation bench.
4, Test the branch sites to main site video conference and the image is very bad, we see the CRC is in the interval 10%-90% from 8020 operation bench.
5,When the branch sites make conference with main site by MCU and the image is very bad, we see the CRC is in the interval 10%-90% from 8020 operation bench.
The CODE light twinkle on the front panel, turn on the terminal H.221 verification software, we can see the CRC is changing in the interval 10%-90%.
Part one: testing
1,At the main site, do the B channel loopback bit error test between 2 BRI in the A company's PBX office, BER=0.
2,At the main site, do the B channel loopback bit error test between BRI and PRI in the A company's PBX office, BER=0.
3,Cut one of the 4 PRI between PBX and N62DDN, connect the TMCP board to SUNSET test instrument to test B channel loopback, use the COBRA test instrument to test bit error at 8020 reference point and find out there was some bit error sometime, replace N62’s TMCP board and retest, BER=0.
4,Test loopback from the main site’s BRI terminal to branch BRI terminal, the bit error is around 10E-05 to 10E-06.
5,Add a DNN node machine at the main conference site, it has the same level to N62 and provide the PRI interface to SUNSET and COBRA test instrument to test point to point loopback at 8020 reference point at the main site.
6,At the main site use COBRA test instrument, at branch site use SS400 test instrument to do B channel loopback test for BRI ISDN terminal interface, node machine PRI interface, office node machine PRI interface, and find the serious slip.
Part two: solution
1, Bind the 3 telephone number which hold 3 ISDN line from A company's switch to form a new number in Hunting Group.
2, The clock tingle of the switch is because the switch clock is set to autosensing sync 0-255. Change the sync setting to 30-100, then the clock in switch and the clock in DDN node machine have the same setting, and could settle the problem.
We test as above in order to eliminate the our device’s problem, then we should to examine the transmission line, switch, node machine.