Alarm

This function block can be used to implement a simple alarm system.

An alarm system consists of at least one sensor and one control unit. The output "Sensor ID" of the sensor is connected to the input "Sensor ID" of the control unit. This also makes it possible to implement multiple alarm systems within one project (e.g. also for indoor and outdoor areas).

Important: This function cannot replace a certified alarm system, but can only contribute to additional security.

Important — disarming belongs at the system itself: Disarming via the visualisation or the APP is not recommended. An intrusion alarm system should only ever be disarmed on site — with a key switch, a code entry or a transponder. Otherwise anyone with access to the APP can lift the intrusion protection; a lost or unlocked mobile device is then enough. Depending on the insurance policy and local regulations, operating it this way may also not be permitted.

It is therefore recommended to switch the Armed/Disarmed input from a device inside the building — for example with a key switch or via the block Block Code switch KNX — and to use the visualisation only to display the outputs Ready, Armed and Alarm. Arming alone via the visualisation is not possible, because every switching command on this input can also disarm the system again. If a control element is created for it anyway, it should be placed on a page that is protected by the user management.

Functional description

Structure. The alarm system consists of a control unit and one or more sensors (window and door contacts, motion detectors, glass break detectors etc.). Each sensor receives a switching state at its input Sensor and reports at its output Ready whether it has triggered. The output Sensor ID of the sensor is connected to an input Sensor ID of the control unit. The control unit thereby knows all the sensors that belong to it and evaluates only those. Several independent systems can be operated in one project (e.g. indoor and outdoor area), each with its own control unit.

States. The control unit has six states. The state results from the outputs:

State	Outputs	Meaning
Disarmed, not ready	BR = 0	At least one sensor has triggered (e.g. a window is open). Arming is not possible.
Disarmed, ready	BR = 1	All sensors are ready. The system can be armed.
Arming pre-warning	SV = 1, SZ counts down	Arming was commanded, the delay is running (time to leave the house).
Armed	SA = 1	The system monitors all sensors.
Alarm pre-warning	SA = 1, AV = 1, AZ counts down	A sensor has triggered, the delay is running (time to disarm after entering the house).
Alarm	SA = 1, AL = 1	The delay has elapsed. The alarm stays until it is cleared.

Sequence.

Becoming ready. The control unit reports Ready (BR = 1) when all assigned sensors are ready. If no sensor is assigned to it, the system is never ready. A sensor with the parameter Always ready never blocks arming (e.g. a motion detector in the hallway).
Arming. The input Armed/Disarmed (SU) arms the system, provided it is ready and is neither armed nor has a pending alarm. The Arming delay runs; during this time SV = 1 and SZ shows the remaining time. If a sensor triggers during this time, arming is cancelled and the system stays disarmed. After closing, arm again. If a sensor is open when the command is given, nothing happens. When the time has elapsed, the system is armed (SA = 1).
Triggering. If a sensor triggers while the system is armed (BR becomes 0), the Alarm delay starts: AV = 1, AZ shows the remaining time. During this time you can disarm, e.g. after entering the house - then there is no alarm. A delay of 0 acts like 1 second.
Alarm. When the time has elapsed, AL = 1 (AV becomes 0). The alarm remains even if the sensor is ready again. A further alarm is only triggered after all sensors have been ready again in between.
Disarming. Disarming is possible in every state except "Disarmed": also during the arming pre-warning (arming is cancelled), the alarm pre-warning (there is no alarm) and during an alarm. If Reset with disarm is set (default), an alarm is cleared in the process.
Acknowledging. The input Reset (RS) clears an alarm. Default: only while disarmed. With Always allow reset also while armed; the system then stays armed. If a sensor is still open, it does not trigger again until all sensors have been ready again.

Operation Armed/Disarmed: edge or level. How the input Armed/Disarmed is evaluated is set by the parameter Operation Armed/Disarmed:

Edge (default) - for push buttons, key switches and code switches that send a pulse. Every positive edge (change from 0 to not 0) toggles: if the system is disarmed and ready, it is armed; in all other states it is disarmed. Falling back to 0 is not evaluated.
Level - for on/off switches that hold their position (e.g. a switch in the visualisation whose state is fed back from Armed). Not 0 means armed, 0 means disarmed. Only the change is evaluated: the position of the switch when the controller starts is only remembered, so that a restart never switches the system by itself. If arming was discarded (sensor open, alarm pending), the switch stays at 1: switch to 0 first and then to 1 again.

A switch with feedback sends a 0 to disarm. With the setting Edge this has no effect - the system stays armed and the alarm cannot be acknowledged. Level is intended for this case.

Examples.

Key switch or push button at the entrance: Operation = Edge, other parameters at their defaults. The key switch arms and disarms; a triggered alarm is cleared by disarming, a separate push button on the input Reset clears it as well.
On/off switch in the visualisation: Operation = Level. The switch writes to Armed/Disarmed, its status comes from the output Armed. A single push button for "Reset" clears an alarm.
Acknowledge the alarm without disarming: set Always allow reset. Useful when the system is to stay armed after a false alarm.
Keep the alarm pending until it is acknowledged: switch off Reset with disarm. Disarming then ends the siren and the pre-warning, but the output Alarm stays 1 until someone acknowledges with Reset. Until then, arming again is blocked.

The outputs SV, SZ, AV and AZ are updated every second.

Sensor

Inputs
SE	Sensor	Sensor that triggers the alarm
Outputs
SD	Sensor ID	ID of the sensor, this must be connected to the input Sensor ID of the control unit.
BE	Ready	Output is 1 when ready. Ready means that the sensor has not triggered (e.g. window closed). The alarm system can only be armed when all sensors are ready.
Parameters
	Detector type	1=Ready: 1 means the sensor has not triggered. 0=Ready: 0 means the sensor has not triggered.
	Always ready	With this parameter the sensor always reports ready even when triggered. This can be used when, for example, a motion detector has triggered while you arm the system but is switched off again after leaving.

Control unit

Inputs
SU	Armed/Disarmed	Arms and disarms the system. How the input is evaluated is set by the parameter Operation Armed/Disarmed. Edge (default): The change from 0 to not 0 is evaluated. If the system is disarmed, it is armed; in all other states it is disarmed. Falling back to 0 has no effect. Level: Every change is evaluated. The change from 0 to not 0 arms, the change from not 0 to 0 disarms. The system is only armed if all sensors are ready and no alarm is pending. Not connected: The system is never armed by itself.
RS	Reset	Clears an alarm. The change from 0 to not 0 is evaluated. While armed, the input only works with the parameter Always allow reset; while disarmed it always works and also cancels arming that is in progress. Optional. Not connected: An alarm is only cleared by disarming (parameter Reset with disarm).
Outputs
BR	Ready	Output is 1 when all connected sensors report ready. The system can only be armed when all sensors are ready.
SV	Arming pre-warning	Output is 1 while the time for arming is running (arming delay).
SZ	Arming time	Remaining time in seconds before the system is armed. If a sensor triggers during this time (Ready becomes 0), arming is cancelled. E.g. motion detectors that still trigger when leaving the house therefore get the parameter Always ready.
SA	Armed	Output is 1 when the system is armed. The output also stays 1 during an alarm.
AV	Alarm pre-warning	Output is 1 while the alarm time is running: a sensor has triggered while the system is armed, but the alarm has not yet been signalled.
AZ	Alarm time	Remaining time in seconds before the alarm is signalled. During this time you can disarm, e.g. after entering the house.
AL	Alarm	Output is 1 when the alarm has been triggered. It stays 1 until it is cleared: by disarming (parameter Reset with disarm, default) or by the input Reset.
Parameters
	Number of sensors	Number of inputs Sensor ID (1 to 32). Each is connected to the output Sensor ID of a sensor.
	Arming delay	Time in seconds to wait before the system is finally armed. E.g. when sensors are triggered by leaving the house.
	Alarm delay	Time in seconds before the alarm is triggered. E.g. when sensors are triggered by entering the house, you can disarm before the alarm is actually triggered.
	Always allow reset	Off (default): The input Reset only works while the system is disarmed. On: It also clears an alarm while the system is armed; the system stays armed.
	Reset with disarm	On (default): Disarming clears an alarm. Off: The alarm stays after disarming and must be cleared with the input Reset; until then the system cannot be armed again.
	Operation Armed/Disarmed	Edge (default): Every positive edge on the input Armed/Disarmed toggles, for push buttons and key switches. Level: Not 0 means armed, 0 means disarmed, for on/off switches with feedback such as in the visualisation.