The Merlin PM2+ is a dual fan current monitor and is to be used in conjunction with the Merlin 1500S, CT1750, 2000S & 3000S Systems; it can be used as an alternative to an air pressure differential switch. The system uses a unique built in current monitor which displays the exact fan current, in order to interlock with the ventilation with precision accuracy. 
 
Ventilation interlock system which isolates the fuel supply if the ventilation fails
Monitor up to 2 extract or supply fans