Motion detectors add a technologically advanced layer of security to your home.

These devices usually come standard in alarm systems purchased from security companies. Monitoring packages may include only one detector or sensor, but in some cases customers can upgrade to get multiple units.

Consumers can also opt for a DIY security system that includes some form of motion detector alarm.

How a motion detector works

The devices are often placed in certain areas – or “zones” – inside a home to monitor interior spaces such as hallways or even entire rooms. Certain models can be used outside the home and connected to outdoor security lighting.

Threat detection

In the past, motion detectors commonly utilized ultrasonic technology that detected threats by sound. Many of today’s devices use infrared technology, sending out invisible beams of light to detect movement within the sensor’s range.


A motion sensor can be controlled using the security system’s keypad or a mobile device, depending on the type of capabilities the system has.

Multiple sensors

Installing a series of motion detectors can provide monitoring for multiple areas of your home. Some homeowners may also choose additional equipment like glass-break sensors to increase their protection.


Most types of motion detectors are battery-operated and don’t require a direct feed. Be sure to check and replace batteries at least once a year to ensure the device is functioning properly.

Types of motion detectors

While there are several types of devices, the passive infrared (IR) motion detector is most commonly used in home security systems. In addition to the infrared type of motion sensor, other options include models that use ultrasonic waves or magnetic pulses.

Other types of sensors that monitor for different home hazards include:

  • Flooding/high water levels
  • Freezing
  • Heat/smoke
  • Carbon monoxide

Motion detectors and alarm monitoring

In monitored alarm systems, two things happen when a potential threat triggers the motion sensor.

The system activates an alarm inside the home (sometimes called a local alarm) and also sends a signal to a monitoring center. One of the center’s dispatch operators responds to the signal, contacting the homeowner to confirm the emergency.

Advanced motion sensor features

Motion detector models vary in price, design and functionality. Different models offer different benefits.

Certain models can be programmed to disregard the movements of indoor pets and reduce the risk of false alarms. This type of motion sensor is often referred to as “pet-friendly” or “pet-immune.”

There are also dual-technology motion sensors, which can interface with other home security equipment. For instance, many security systems include surveillance features such as security cameras. The more advanced systems may offer the option of motion-activated cameras.

With this type of feature, an outdoor camera can be programmed to start recording when a motion sensor detects movement.