If your barrier gates have an access control system, then there should also be a way for visitors to enter too. This allows residents or employees to receive guests and services such as plumbers or pest control. A common solution to this problem is a call button. Upon arrival, guests have the system call their host to let them inside the gate. This helps prevent any uninvited guests from entering the complex.http://www.gatexpertstore.com/....parking-barrier-gate