The mechanical differential pressure switch / differential pressure monitor PREMASREG® DS-2 with 4-hole plastic base ring, is used for monitoring above-atmospheric, differential and below-atmospheric pressure of clean air, gaseous, non-aggressive media in air ducts, air intake or exhaust devices. As a flow monitor, differential pressure governor, pressure controller for flow monitoring at electric heating registers as well as for monitoring V-belts and filters, as air pressure deficiency protection for monitoring ventilators, dampers, or as a limit value controller. Switchpoint adjustment is done internally using the internal precision scale. These instruments are factory-calibrated.