TDM

From FreeSWITCH Wiki

Time-Division Multiplexing (TDM) is a type of digital or (rarely) analog multiplexing in which two or more signals or bit streams are transferred apparently simultaneously as sub-channels in one communication channel, but are physically taking turns on the channel. The time domain is divided into several recurrent timeslots of fixed length, one for each sub-channel. A sample byte or data block of sub-channel 1 is transmitted during timeslot 1, sub-channel 2 during timeslot 2, etc. One TDM frame consists of one timeslot per sub-channel. After the last sub-channel the cycle starts all over again with a new frame, starting with the second sample, byte or data block from sub-channel 1, etc.

The above is taken from the TDM entry on Wikipedia. For the complete article on TDM follow this link.

OpenZAP is a driver that is capable of interfacing with both analog and PRI cards. The project implements a TDM abstraction library to provide an interface to TDM hardware as well as various signaling for T1/E1 interfaces.