Complex sentence: A solitary security guard was stationed near the entrance to prevent trespassing, and two security personnel are assigned round-the-clock duty to prevent unauthorised people and vehicles from entering.
Split into simpler sentences: A solitary security guard was stationed bear the entrance to prevent trespassing and encroachment by unauthorised people. It is also learnt that two security personnel are assigned round-the-clock duty to prevent unauthorised people and vehicles from entering.