I guess you need some information on the  IP system（as SIP system） and TDM interworking, below for your reference:

1.        IETF  RFC3666 : Session Initiation Protocol (SIP)  Public Switched Telephone Network (PSTN) Call Flows （ http://datatracker.ietf.org/doc/rfc3666/?include_text=1）

2.        ITU-T Q.1912.5 : Interworking between Session Initiation Protocol (SIP) and Bearer Independent Call Control protocol or ISDN User Part

3.        ETSI  TS29.163: Interworking between the IP Multimedia (IM) Core Network (CN) subsystemand Circuit Switched (CS) networks

Mr. Meng

Thanks for the references.

I'll take a in-depth look into them.

Best Regards.

there are simple books from cisco, such as, DSL and Fiber-Optic Technologies. in the first chpters they talk about what you are asking for