programmable logic controller u201c plc u201d not shown the plc may then use the sensor input to determine whether to deploy and retract the doors 36 38 depending upon preconfigured logic for example clutches and the drive 44 may be controlled by the plc that is based upon the state of the sensors the drive 44 can be energized a clutch engaged and a door opened ideally four or more sensors would be incorporated to determine the presence of objects e g machinery workers merchandise and the like approaching within and exiting the doorway 10 thus turning to fig2 a first sensor 68 is located in zone a and is adjacent to the first door 36 a second sensor 70 is located within the air curtain 18 proximate to the first door 36 a third sensor 72 is located within the air curtain 18 proximate to the second door 38 finally a fourth sensor 74 is located in zone b and is adjacent to the second door 38 greater or fewer sensors may be used depending upon the sensor accuracy and desired coverage the preferred embodiment includes sufficient sensors to determine when an object is approaching either door 36 38 from zone a or zone b or from within the air curtain 18 a non exhaustive example of the door control will be described as an object approaches the doorway 10 from within zone a the first sensor 68 detects its presence and sends a signal to the plc the plc energizes or de energizes the driver 44 drivers and clutches depending upon the embodiment in use and causes the first door 36.