Scion xb car alarm is an electronic device installed in a vehiclein an attempt to discourage thef tof the vehicle itself. Its contents, or both. Car alarms work by emitting. High-volume sound(usually a siren, klaxon, pre-recorded verbal warning, the vehicle's own horn, or acombination thereof) when the conditions necessary for triggering are me as Well as by flashing some of the vehicle's lights, and (optionally) notifying the car's owner via a paging system  and interrupting various electrical circuits necessary for the car to start xb .

• Almost all OEM alarms are typically armed xb and disarmed with the vehicle's keyless xb entry remote. On many xb alarm vehicles the key cylinders in the driver or front passenger door activate switches, so that when a key is used in the door the alarm will arm or disarm. Some vehicles will arm xb alarm when the power door lock switch is pressed with the driver's door open, and the door is subsequently closed. Some vehicles will disarm if the ignition is turned on xb often when the vehicle is equipped with a key-based immobilizer and an alarm, the combination of thexb   valid key code and the ignition disarms the system.The simplest aftermarket alarms are one-piece units with a siren and control module. Such a unit will typically contain a shock sensor and two wires (12 volt constant power and ground) which are connected to the car's battery. This type of alarm is triggered by vibration transferred to the shock sensor, or by voltage changes on the input (the alarm assumes that a sudden change in xb voltage is due to a door or trunk being opened, or the ignition being turned on); however it is very prone to false triggers on a late-model vehicle with many electronic control modules, which can draw xb alarm current with the car off. For this last reason these alarms are increasingly becoming obsolete xb alarm