> For the complete documentation index, see [llms.txt](https://help.security.gallagher.com/smb/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.security.gallagher.com/smb/installing-gallagher-smb/installing-the-hardware/data-communication.md).

# Data Communication

Good communication through proper cabling is crucial. The right cabling not only guarantees system reliability but also enhances security and efficiency. In addition, we've invested in our own communications protocol, HBUS, so our system provides the fastest communications and selecting the right cable maximizes that capacity.

<details>

<summary><mark style="color:orange;"><strong>Compatibility</strong></mark> </summary>

HBUS runs over a wide range of common security and IT network cabling, but it is important to ensure the cables are suitable for a system's specific devices and environment.

</details>

<details>

<summary><mark style="color:orange;"><strong>"Daisy Chain" topology</strong></mark></summary>

The cabling standard should be maintained throughout the installation: controller to devices, and devices to devices. The cabling between HBUS devices should be done in a "daisy chain" topology. This means that installers need to install end-of-line terminating resistors (typically 120 ohms) to match the transmission line impedance and prevent signal reflections.

<figure><img src="https://521511078-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fj78FgrliX8rYCdK2hg8n%2Fuploads%2Ft2mOgYX9xlkWYS9t64Fk%2FDaisy%20Chain.png?alt=media&amp;token=ee066efc-b700-411a-89f9-25aab4723b9f" alt=""><figcaption></figcaption></figure>

</details>

<details>

<summary><mark style="color:orange;"><strong>Scale &#x26; Distance</strong></mark> </summary>

The HBUS protocol allows communication over distances up to 500 meters (1640 feet). This is beneficial for large installation where devices are spread out but ensure that the cables used support the required impedance, 120 ohms, particularly if you are dealing with long distances.

</details>

<details>

<summary><mark style="color:orange;"><strong>Terminating</strong></mark> </summary>

Devices should be connected one after the other, like a daisy chain, to prevent signal reflections. &#x20;

The Technician will need to terminate both ends of the daisy chain to prevent signal reflection.

If terminating in the Controller, terminate by leaving the termination jumper in positions (or inserting to the correct slot if previously removed) in the Controller.

If terminating at device, like a reader, terminate by joining the orange and green wires.

<figure><img src="https://521511078-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fj78FgrliX8rYCdK2hg8n%2Fuploads%2FSktY4gha6dICA5PxI6dE%2Freader%20wrie%202.jpg?alt=media&amp;token=cdd00982-7c9b-4fdf-a0c3-997cb73e88a5" alt=""><figcaption></figcaption></figure>

</details>


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