Local end loopback, which means that data goes through a loop within a NodeB (or RNC) instead of through E1 cables. It     is used to check whether the transmission chips are normal.

After we execute the SET E1T1LOP as REMOTE mode on A side, we can execute DSP E1T1 on B side to query E1 state, if the state is normal, that means the physical transmission from A to B is normal, otherwise, it means the transmission is faulty.

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