Only one TCM can be used at one site

The scope of management of OMSn is the path from the input optical port on the multiplexer unit of the sending site to the output optical port on the multiplexer unit of the receiving site, called the optical multiplexing segment (OMS) path.

Which of the following statements regarding multiplexing partial remote error indication (MS-REI) is correct?
(1) B2 bytes indicate the transmission channel.
(2) The M1 byte represents the transmission channel
(3) THE MS-REl is sent from the receiver to the source.
(4) MS-REI is transmitted from the source to the receiver.
(5) Indicates the number of bit errors detected by the receiver after receiving the MS signal.

For OSN3500, there is a slot mapping relationship between the processing board and the interface pre-processor. The processing board in slot 1 maps to the interface board in slots 19-20.

TU-AIS is often encountered during network maintenance. Which of the following alerts can trigger a TU-AIS alert? (Multiple choice).