Basic Principles
The User presents their Card or Token to the Reader. This information is sent to the Controller. The Controller then Validates the Card, by checking

Is the Card is Valid on its Card Database.
Is it authorised to open the door (Access Group)
Is the Card authorised during this particular time period (Time Zone).
Once the criteria of all three are met it then releases the Lock to allow access through the door, and the opening of the contact is ignored

The Card number and the Reader number is then sent to the Computer and found on its database, which is listed with a Users Name. The Users name,Card number,Reader, and time it was used is sent to the "History File" or "Transactions Log", to be stored and also displayed on the monitor screen.

Should the door be forced open, the contact is therefore opened without a Valid Card. The Controller would then send this information to the Computer indicating "door forced" and generate and Alarm Condition on the screen and/or a sounder alarm.

The PTE (Press-to-exit) button  located on the secure side of the door, when pressed. is a valid to exit the door therefore to contact is again ignored  and the lock is unlocked to allow exit. Again pressed should the door be forced open from the inside , the contact is therefore monitored as being open without Valid egress.