> For the complete documentation index, see [llms.txt](https://help.boomerang3.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.boomerang3.com/boomerang-2-system-administrator-manual/boomerang_system/infrastructure_modules.md).

# Infrastructure modules

The Boomerang system can use the following infrastructure modules for measurements acquisition. The infrastructure modules are called ‘PC nodes’ in Boomerang system.

| PC node                       | Measurement transmission initiated by: | Measurement received in B2 system by: | Measurement delivered to B2 system via: | Connection to sensor node      |
| ----------------------------- | -------------------------------------- | ------------------------------------- | --------------------------------------- | ------------------------------ |
| S2 PC node                    | B2 server                              | B2 server                             | Serial Port or Virtual Serial Port      | 433MHz S2 radio                |
| S3 PC node                    | B2 server                              | B2 server                             | Serial Port or Virtual Serial Port      | Built into infrastructure node |
| S2 Gateway (S2GW)             | S2GW                                   | B2WEB server                          | HTTP - POST method                      | 433MHz S2 radio                |
| BoomBridgeOne (BBO)           | BBO                                    | B2WEB server                          | HTTP - POST method                      | Built-into infrastructure node |
| Boomerang Backup Logger (BBL) | BBL                                    | B2WEB server                          | HTTP - POST method                      | Built into infrastructure node |
| CoolGuard Gateway (CGGW)      | CGGW                                   | B2WEB server                          | HTTP - POST method                      | 433MHz CG radio                |
| ICU Logger                    | ICU Logger                             | B2WEB server                          | HTTP - POST method                      | Virtual sensor node            |


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