Complete Guide to Door Contact Sensors

Door contacts represent some of the most popular sensors that are used with alarm systems. Nearly every setup will incorporate these devices in some form. After all, knowing when a door has been opened is critical for most systems. But there is a lot to consider when choosing door contacts.

A door sensor is a device that is used to let an alarm control panel know when a door has been opened. When this happens, the system will respond depending on panel's current arming state and the programming settings for the zone. Some popular responses for door contacts include requiring a system disarm within the entry delay period, producing a simple chime and triggering an immediate alarm. These responses are present with virtually any door contact and system setup. A previous blog post of ours actually covers the Response Types for door sensors in greater detail. We recommend checking out that post for more information. But while the general functionality is the same across almost any contact, selecting the best option for your system might seem overwhelming.

Perhaps the first thing you should consider is whether you want a hardwired contact or a wireless contact. A wired contact will communicate with the panel through a direct hardwired connection. A wireless contact will communicate with the panel through wireless RF signals. The advantage to a wireless sensor is that it will be much easier to set up, since no wires will need to be run from the system to the sensor. But some users prefer hardwired sensors, as they essentially become a fixture for the building itself. Another advantage to hardwired contacts is that they don't use batteries. This means that a user will never have to buy new batteries for their hardwired contact. There are all types of door sensors in both the hardwired and wireless variety.

If you choose a hardwired contact, you will need to have a hardwired zone available on your system. Most hardwired contacts can be used with nearly any system that supports hardwired sensors. On the other hand, if you choose a wireless contact, you will need to have a wireless zone available. You will also need to make sure the wireless contact communicates at an RF frequency that is compatible with your system. Knowing which wireless RF signals are accepted by your alarm system is very important for getting sensors to work properly. Some of the most popular RF signals used by alarm systems include 319.5 MHz, 345 MHz, 433 MHz, 915 MHz and 2.4 GHz. Remember to always make sure the wireless door contact you choose operates at a frequency that works with your alarm system!

Another major distinction for door contacts is whether they are surface-mounted or recessed. A surface-mounted contact is visible on the outside of the door. A recessed contact is hidden inside the door and its frame. As a general rule, surface-mounted contacts are easier to install, since no holes need to be drilled. But the advantage to recessed contacts is that the end result can appear neater, since no sensor will be visible. We generally recommend that users installed surface-mounted sensors, due to the fact that they are easier to install and generally offer more reliable performance.

With that in mind, door sensors can be assigned to one of four major categories. These are wireless surface-mounted contacts, wireless recessed contacts, hardwired surface-mounted contacts and hardwired recessed contacts. Regardless of which category a door contact is assigned, these devices generally all work in the same way. Most door contacts consist of a sensor and a magnet. The sensor is installed on the stationary portion of the door frame, while the magnet installed on the moving portion of the door. In most cases, the magnet must be within a half-inch of the sensor. Placing the sensor itself on the stationary portion of the door helps prevent it from being damaged when the door is opened or closed. Once the door is opened, the magnet will separate from the sensor and cause a reed switch inside the sensor to activate. The sensor will then alert the system to let it know that the door has been opened. Please note that there are a few door sensors that are exceptions to this general operation. Namely, recessed sensors that use a plunger switch, like the wireless Honeywell 5800RPS and the hardwired Honeywell 956RPT.

Before we get into general door contacts that would be used for most applications, we want to make special mention of some more unique sensors that would be used for specific setups. Honeywell offers many hardwired wide-gap contacts that can be used with garage doors and industrial applications. The advantage to these sensors is that they can utilize a much larger spacing gap between the sensor and magnet than what is possible with standard door contacts. We have seen some industrial contacts where the spacing gap can be up to 2.5 inches. That's five times the recommended maximum spacing gap for standard door contacts! Some examples of these industrial-grade hardwired contacts include the Honeywell 958, the Honeywell 968XTP, the Honeywell 959, the Honeywell 958-2, the Honeywell 950W, the Honeywell 960 and the Honeywell 7945. Many of these industrial-grade contacts are also suitable for outdoor use. Another option for a garage door is to use a tilt sensor, like the Honeywell 5822T or an Interlogix TX-E401.

But if a user requires a wireless contact for an outdoor application, there only option is really the Honeywell 5816OD. This wireless contact offers a recommended maximum spacing gap of 1.5" inches, and it is great for use with fences and outside doors. It has a nominal range of 200 feet when used with most systems. As a 345 MHz Sensor from the Honeywell 5800 Series, it will work with nearly any Honeywell Alarm System.

If you don't require an industrial or an outdoor contact, you will most likely be able use a relatively standard contact with your alarm system. We prepared a table below that outlines many of the most popular and widely used door contacts sold by Alarm Grid. Please note that not every contact is included - there would be too many to list! But this is a good chart to help you find the perfect sensor for your system.

If you're still having trouble deciding on the perfect door contact for your alarm system, our experts are always happy to help. You may email us at support@alarmgrid.com, and we will get back to you as soon as possible. You may also call us at (888) 818-7728 during normal business hours, which are 9am to 8pm EST M-F. We look forward to hearing from you!