# Network structure The radio network consists of: 1. One PC node. 2. Measuring node(s). 3. Linking node(s). The node that is in the center of the star network is called PC node and it works as a connector between the radio network consisting of the measuring and linking nodes and the monitoring system server. The measuring nodes are equipped with a sensor or sensors. The linking nodes are used to forward the radio frames to the other nodes and enable transmission on longer distances. Any measuring node may be used as a linking node or a node without a sensor may be used for this purpose as well. The PC node receives commands from the server (in case of B2) or from S2GW (in case of B3). Some of them are transmitted over radio. The command is received by an addressed node which sends an anwser that is received by a PC node and transmitted back to the server. The PC node is connected either directly to the server COM port or to a virtual serial port created using [Digi](https://www.digi.com/products/networking/infrastructure-management/serial-connectivity) or [Tibbo](https://tibbo.com/store/controllers/ds203.html) modules. A single B2 server may handle 254 radio networks. A single B3 server may handle 254 radio networks per root group. The commands are described in [S2 communication protocol](/s2-radio-system-manual/s2-system-description/s2-node/s2-communication-protocol.md). --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://help.boomerang3.com/s2-radio-system-manual/s2-system-description/network-structure.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.