Solution:

There are little different between the isolation and surge protection. The main character of isolation is the electrical circuit can be tore in two part, one is the receiver side and another is the computer side. The main reason of choosing isolation is to protect the other cards on the same backplane, since the separate of circuit can prevent the abnormal signal from influencing the whole system. On the other hand, the function of surge protection is mainly to protect the parts which are connecting with the input signal. And we need it in case the input signal is with a electrical spike which will damage the receiver. However, its capability of protection is rather limited than the isolation. Since sometimes when the surge is too huge not only the receiver will be damaged but also the whole system is in danger.