The VESDA ModBus High Level Interface (HLI) links your VESDAnet with PC software monitoring tools, Building Management Systems (BMSs) or Fire Alarm Control Panels (FACPs), otherwise known as host, that support the ModBus protocol.

One ModBus HLI is used to interface to a VESDAnet. Modbus HLI supports up to a maximum of 40 VESDA detectors on a VESDAnet.The Modbus HLI supports VESDAnet detector zone numbers between 1 to 200. The Modbus HLI divides up the address range into to 7 logical networks. For example the first 30 addresses are considered in network 1, addresses between 31 to 60 are in network 2 and so on.

Smoke and Alarm Levels

The Smoke Level is reported relative to the Fire Alarm threshold where the full scale is 20. For example, if the Fire Alarm threshold is 0.5 %obs/m, a level of 0.1%obs/m is reported as 4. In other words, the Actual Smoke level = (Reported smoke value Fire Threshold) / 20.