how often a trigger is fired

how often a trigger is fired in vera. there is a setting for trigger ?
for instance:
Assuming that a thermostat indicate current temperature is 17 and there is “temperature goes below 17” trigger. So as soon as temperature drop below 17. trigger will be fired once. and if temperature continuous dropping to 16 or 15, would trigger be fired again?

The value has to cross the threshold for it to trigger. It doesn’t matter how low it goes, it would have to rise above 17 and fall below it to trigger again.

oh thanks for info