All transducers have a noise floor. This means that there exist a level where the transducer will output its own noise instead of the physical situation.

To aware the user of this, an underscale spectrum can be defined. For each frequency, the lowest reliable level readings from the transducer at this frequency may be registered.

In SLM view, an underscale condition will be indicated with a less-than symbol besides the reading.

The underscale spectrum can be loaded by using .xml file located on the SD card. The filename must be 'NetworkUnderscale.xml'. A default file can be downloaded from the Norsonic homepage, www.norsonic.com/downloads.