LLSSA Lv 1 Flashcards
What is a “normally open” contact?
a contact with a single switch and a single magnet, when the switch is near the magnet it stays closed, when the magnet moves away it opens. Normally open contacts are used in a closed circuit loop.
What is “Normal”?
A sensor is usually marked as normal when no force or power is applied to it.
What is a “normally closed” contact?
A close contact has a single switch in a single magnet, when the switch is near the magnet it stays open, when the magnet moves away it closes. normally closed contacts are used in an open circuit loop.
What is a balanced contact?
A contact switch used to reduce the chance of bypassing contact with a third magnet, an additional magnet is placed inside the switch assembly to balance the external magnet.
What is a gap rating?
The distance that the contact and magnet can be separated before the switch activates, a larger gap will allow the door to adapt to vibrations or warping of the door.
What does PIR stand for?
PASSIVE INFRARED sensor.
How does a PIR work?
The Fresnel Lens focuses thermal energy on the PIR sensor, sensor outputs electricity based on what it sees, amplifier boosts low amounts of electricity to usable level, comparator circuit decides when to trigger sensor output, output is used to report to the alarm panel.
In a normally closed zone, when does the sensor trigger the alarm?
When the flow of electricity through the circuit loop stops. (The circuit is normally closed, allowing current to flow back to the panel, when the flow is interrupted, the sensor reports an alarm).
In a normally open zone, when does the system trigger an alarm?
When the circuit is closed and electricity is allowed to flow back to the panel, triggering an alarm.
