Exit / Entry Zone & Buzzer

The alarm described so far is a very basic system. For it to work in practice it will have to have a method to enable the operator to enter and leave the premises without activating the system, but still protecting the exit/entry route. For this reason most control panels will incorporate a special zone called an “exit/entry zone”. This zone operates in almost exactly the same manner as the detection loop previously described, except that there is a time delay on it.

How it works:

When the operator sets the system a small buzzer will sound for a preset period. (Usually between 15 and 45 secs). During this time the detectors connected to the exit/entry zone will not activate the system until the period has elapsed. This allows the user to exit the premises via a designated route, called the exit/entry route. All detectors on this route are connected to the exit/entry zone. After the preset period, the buzzer will stop and the ex/en loop must be closed. By this time the operator will have vacated the premises and the alarm is now fully set.

On returning, once a detector on the ex/en zone is opened, this will initiate the ex/en timer. Again a preset time between 15 and 45 secs. Is given to allow the operator to enter and switch the system off.

Over-leaf is show, the terminal block for the control panel with the connection for the ex/en zone and the ex/en buzzer. This buzzer is a 12 VDC type and the panel will provide a 12 VDC output for the ex/en period. The time delay is set by two “potentiometers”, usually referred to as presets. These are normally mounted on the PCB and are rotated by the use of screw driver to the correct setting.

All detectors that the operator must pass to enter and leave the premises are connected to this loop.

In practice the amount of detection devices on this zone are kept to a minimum and if possible just one detector, that being the front door (final door).

The buzzer can be mounted inside the panel but if it is a case Where this may not be heard from the front door then it can be Located outside the panel in a suitable position. The function of this buzzer is to warn the operator that the system is going to Set/activate after the preset period.