VESDA Open Protocol High Level Interface

The VESDA Open Protocol High Level Interface (HLI) links your VESDAnet with PC software monitoring tools, Building Management Systems (BMSs) and Fire Alarm Control Panels (FACPs), otherwise known as ‘host’.

Open Protocol HLI Models

There are two models available, depending on whether you require communication between your host and VESDAnet to be master-slave or peer-to-peer.

VHX-0310 Open Protocol HLI (master-slave)

In the master-slave model, the host supervises the communications link between itself and the HLI (slave) by regularly polling the HLI to determine whether there has been a change in the status of a detector on VESDAnet. In response to polling by the host, the HLI generates a single response which is sent back to the host. In this way, no unsolicited messages are sent from
the HLI to the host. Depending on the polling strategy adopted, the Master/Slave Open Protocol HLI is able to report any and all fire alarms within a few seconds of a detector going into alarm. Exact performance is dependent on the polling strategy adopted.

VHX-0300 Open Protocol HLI (peer-to-peer)

In the peer-to-peer model, the host polls the HLI for information about devices on VESDAnet, while the HLI sends unsolicited messages to the host. In this way, both the HLI and host are responsible for supervising the communications link between them.
In the peer-to-peer model, the host can request and receive multiple messages from the HLI.