Access system in restricted areas based on programmable logic controller and GSM modem

The paper presents the control of a retractable pole operated by phone call that allows access to a restricted area or a parking lot. The remote control is one or several mobile phones whose numbers have been introduced in the program of a programmable logic controller. The phone numbers are the passwords that allow access to the area. The system works as an agenda that allows access on certain days and hours. Different kinds of alarms can also be installed. The application, developed in laboratory for teaching purposes, can be easily implemented on the spot.