 Pressure sensitive sensors that count walk-ins based on the number of footsteps on a pressure sensitive platform or mat were used as well.The first UK beam counters were installed by Business Blueprints in 1988 at Meadowhall centre, outside Sheffield, Yorks.They covered all 14 entrances and recorded footfall of 20 million shoppers p.a.Daily manual checks were made to recalibrate each beam counter, leading to an error rate of +\-3%, significantly more accurate than later, video systems.