> 2.1 | Product Concept and Architecture

> The multiplexer mode enables one serial interface to transfer data to or from three different host applications. This is achieved by providing three virtual channels running the multiplexer protocol.
> For example, multiplexer mode allows the user to make a call (voice, fax, data or GPRS) on one channel and, at the same time, to control the module and even send or receive short messages on other channels, without disturbing the data flow on either channel. This is of great advantage when several independent electronic devices or interfaces are used.
> To access the three virtual interfaces, both the GSM engine and the host application must contain Mux components which communicate over the multiplexer protocol.
> In multiplexer mode, AT commands and data are encapsulated into packets. Each packet has a channel identification and may vary in length.
> Note: All statements regarding GPRS are valid only for Siemens wireless products capable of GPRS.
> Figure 1: Multiplexer architecture