2 Building Safety Technologies
2.1 Access to the Building

The first step towards building security is Access Control System. The access can be granted globally for the entire building or selectively for defined parts of the building.

In the role of the actuators, doors and turnstiles are used. Historical development began with mechanical security locks. Due to the fact that a mechanical key can be easily counterfeited or even stolen, mechanical locks are not recognised as sufficient to meet modern access control requirements.

The keys are being replaced with electronic chips in the form of pendants, usually containing a passive RFID tag. The sensor at the door identifies the key holder through wireless communication and transmits this information to a central server, which stores the database of chips. The server contains a list of permissions (according to Access Control List), which is programmed to allow the chip holder access only to the areas where the holder is allowed to access, and in times when the holder is allowed to access them. Identification cards are used for building entrances in a similar way. Unlike mechanical locks, it is possible to block the access after reporting the chip or identity card loss. Very often we can see association of an access control system with attendance control system. Generally we speak about Identity Management Systems.

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Fig. 2.1: Doors Security

Explanation:

  1. Card or chip reader is placed on both sides of the door
  2. Electric lock
  3. Door contact
  4. Emergency escape button is placed on both sides of the door

The normal state for the door is when it is closed and the door contact (3) sends a signal confirming that. A person who wants to enter is identified by chip or card. The reader transmits data to the control unit, where the identification code is compared to the list of permissions. In the case that a match is confirmed (relational operation of equivalence), an impulse is sent to open the electric lock. The impulse keeps the lock in the open position for a predefined time, e.g. 10s. A person opens the door and enters, which is indicated to the system by changing the state signal on the door contact. If the door opening time is shorter than the predefined one, changing of the state of the door contact ensures relocking of the door. If a person tries to enter without authorization, the door remains locked; in such case the attempt for unauthorized entry can be recorded in the system. The reading device usually provides feedback on allowing or denying the access, using either coloured LEDs or voice announcement.

During the operation of the building, states of emergency can occur. One of them is when the door contact is not sending a signal that the door is closed. The door may be secured by a wedge or have failed to close and lock. In both cases, the control unit sends an alarm message to the operator and the door must be checked on the spot. Another state of emergency occurs when it is necessary to open an emergency door during a fire alarm or when emergency medical care is needed for people inside the building. For this purpose, the emergency escape button should be used to unlock the door. The use of emergency escape button is also recorded on a central server.

Technologies providing access depend on the type of the reader. Readers can be divided into three categories:

Basic (non-smart) card reader simply reads the card number and PIN, and transmits it to a control unit.

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Fig. 2.2: Semi-intelligent card reader operation

Semi-intelligent card reader is linked directly with all the inputs and outputs necessary for monitoring of the door’s hardware (electric lock, door contact, emergency escape button – see Fig. 2.2). Semi-intelligent reader does not make any decisions on the access.

Intelligent card reader is linked directly with all the inputs and outputs necessary for monitoring of the door, like the semi-intelligent one. Unlike semi-itelligent reader, it also has a memory and computing capabilities necessary to make decisions on the access independently of other devices.

Some readers are equipped with additional features, such as LCD displays and function keys for other inputs and outputs (camera, microphone, etc.).