Time Division Switching: A switching element can be shared by number of simultaneously active speech circuits. This is the principle of time division switching. Obviously, with the way the switching elements are shared in time division switching, much greater savings can be achieved in the number of switching elements when compared to multistage space division switching.
Basic Time Division Switching: The functional blocks of a memory based time division switching switch is shown in Fig. and its equivalent circuit in Fig. In this organisation, the data coming in through the inlets are written into the data memory and later read out to the appropriate outlets. The incoming and outgoing data are usually in serial form whereas the data are written into and read out of the memory in parallel form. It, therefore, becomes necessary to perform serial-to-serial conversion and parallel-to-serial conversion at the inlets and outlets respectively. For convenience, the data-in and data-out parts of the MDR are shown separately for the data memory in Fig. 6.5 although in reality, MDR is a single register . Since there is only one MDR, a gating mechanism is necessary to connect the required inlet/outlet to MDR. This is done by the in-gate and out-gate units.