signaling gateway, how it works

hi folks,

suppose i have a signaling gateway that connects to a gateway MSC in a IS-41 network on the TDM side (through SS7 over a E1 link) and on the IP side connects to a softswitch (SIGTRAN). i'd like to understand how it suppose to coupled the voice signals from the TDM side to the IP side (or vice versa) (ie how's the conversion carried out between SS7 and SIGTRAN?)

i hope someone can enlighten me on this in a layman's view of the things.

thanks in advance.