There is no relay sound in the decoder.
1. Check whether the decoder is powered;
2. Check the code converter is pulled to the output 485 signal;
3. Check whether the decoder protocol is set correctly;
4. Check if the baud rate setting is consistent with the decoder (check the address code settings and the selected camera is the same (detailed address code dial table see decoder manual);
5. Check the decoder and the code converter wiring is wrong (1-485A, 2-B; some decoder is 1-485B, 2-A);
6. Check the decoder work is normal (the old decoder power off after a minute power, whether there is self-test sound; software control PTZ, the decoder UP, DOWN, AUTO and other ports and PTCOM port will be between the voltage changes, The situation according to the decoder 24VOR220V, some of these ports will have the decoder switch signal changes), if the decoder is working properly, otherwise the decoder failure;
7. Check if the fuse of the decoder is burned out.