完成A接口倒换后，BSC出现2992错误（BTS AND TC UNSYNCHRONIZATION CLEAR CALLS ON A INTERFACE alarm），说明A接口可能存在哪类问题（）
- AA interface exist crossconnect circuit
- Binconsistent CCSPCM between BSC and MSC
- CA interface exist loop circuit
- Dinconsistent circuit number in circuit group between BSC and MSC