Add $175.00 for FREE shipping
Learn More!
Sensor Type
Door / Window
Contact Closure / Relay
Outdoor Rated
Normal State
Normally Open
Ease of Installation
Beginner (Installs < 10 minutes)
Other Ways to Shop
Customer Favorites
In Stock
On Sale
Order the Smarthome Catalog

Magnetic Sensor Integrates Into Just About Any Security System, Alerts You Of Possible Property Intrusions
SECO-LARM SM-300Q/WH Surface Mount Magnetic Contact Switch, Normally Open
SECO-LARM Enforcer SM-300Q/WH Surface Mount Magnetic Contact Switch, Normally Open
Click for larger image and other views
Click for Larger Diagram Contacts installed on a window Contact Dimensions
SECO-LARM Enforcer SM-300Q/WH Surface Mount Magnetic Contact Switch, Normally Open
Item# 7040
Price: Normally $5.99 
Hot Deal $2.93
Free shipping on orders over $175 - See Details


  • Works with nearly all standard, hardwired alarm systems
  • Designed for use on Normally Open (NO) applications
  • Use on doors, windows, and sliding doors
  • UL Listed for security systems
  • 3/4 inch Operation gap

Essential Info

The SECO-LARM Enforcer SM-300Q/WH Surface Mount Magnetic Contact Switch is ideal for any normally open location and sends an alert signal to your security system when it is no longer in a normally open state. Simply mount the magnetic sensors on a door or window so that the two are in contact with each other when the door or window is closed. Breaking the connection between the two sensors triggers an alert thus notifying your property's security system. Slotted mounting holes make it easy to adjust the distance between the magnet and the sensor, with a maximum operational gap of 0.75 inches. Measuring 2.48 inches long and half an inch high, they can be attached with wood or sheet metal screws, sold separately. The switch is waterproof and mounted in a high-impact plastic case. The rhodium plated contacts handle up to 100mA at 100 volts DC and are rated for 50 million openings and closings. It can reliably operate in temperatures between -15°F and 160°F. The sensor's maximum operational gap is 0.75 inches.


What's Included

  • 1x - Set of Surface Mount Magnetic Contact Switches, Normally Open
  • 1x - Owner's Manual
  • More Info

    This Normally Open Surface Mount Magnetic Contact Switch is also available in a 10-Pack.

    A Normally Closed Surface Mount Magnetic Contact Switch is also available



    Manufacturer Product No.:SM300Q/WH
    Weight:0.05 pounds
    Dimensions:2.48 inches x 0.5 inches
    Compatibility:Closed circuit systems

    Important notes:
    Defective exchanges for identical item within 30 days of purchase. After 30 days, please contact the manufacturer.
    Manufacturer contact information: SECO-LARM USA Inc, Tel: (949) 261-2999


    Click for Larger Diagram  Contacts installed on a window  Contact Dimensions   
    Click for Larger Diagram  Contacts installed on a window  Contact Dimensions   


    116 Ratings
    5 star: 71%  (82)
    4 star: 17%  (20)
    3 star: 5%  (6)
    2 star: 3%  (3)
    1 star: 4%  (5)
    Average Customer Rating
    (116 customer ratings)
    Share your thoughts with other customers
    THOMAS A. -- milwaukee, WI   5/29/2014
    ordered for a future project
    WM -- winfield, IL   5/15/2014
    Do not work as described
    WILLIAM -- palmetto bay, FL   1/12/2014
    Original shipment recieved contained the wrong quantities of the correct product, follow up shipment cprrected the mistake.
    MICHAEL -- leduc, AB   11/27/2013
    This didn't work for me. I don't know is this is only some products. I was try use that for everspring z-wave door/windows sensor. I try different magnetic contact it was skylink products(old security system) it work well
    LINDA -- stanwood, WA   10/21/2013
    The part works great. It did take a while to get it because it was backordered. Our source for this type of part no longer carries this so we appreciate that you have it.
    ANTHONY -- jackson, NJ   3/21/2013
    KEVIN -- brooklyn, NY   1/19/2013
    Perfect! Installed on closet door, to control lights inside closet, kinda like refrigerator light (NYC electrical code doesn't allow regular light switches in closets). Works like a charm, with a controller. It's rated for 3/4", but my experience shows it's a bit more sensitive than that. Which is a good thing. Note that "normally open" is the opposite of how most other vendors use the term. "Normally" here means "when the magnet is next to the switch", not "when the magnet is far away".
    STANLEY -- redondo beach, CA   12/28/2012
    Exactly what I wanted. Operates as expected. Good shipping time and process
    ROBERT -- san francisco, CA   12/21/2012
    Not really that much to say. The relay is open when the magnet is near, and closed when they're apart. It works.
    KIRK -- north dighton, MA   11/26/2012
    these work fine
    PETER -- duncan, BC   11/19/2012
    Works great but I wished they were a little smaller.
    EDWARD -- cedar knolls, NJ   8/18/2012
    Worked as expected. Activates with about 1" gap. I wish they had a micro version (1") that did the same thing!
    GEORGE H -- rockledge, FL   4/21/2012
    Exactly as described and wanted. Delivered ahead of schedule.
    MICHAEL -- belchertown, MA   3/21/2012
    Items were not in stock when ordered, so had to wait quite awhile for delivery. However, the magnetic switches were very reasonably priced. Worth the wait,...
    JULIA -- ridgway, CO   3/21/2012
    Ditto for the above
    BOB -- wellborn, FL   2/17/2012
    WILLIAM -- lone tree, CO   2/13/2012
    Works perfectly with my home security system.
    VINCENT -- fairfield, CA   2/2/2012
    Work great
    VINCENT -- fairfield, CA   1/12/2012
    Works as advertised
    ERIC -- metamora, MI   1/9/2012
    Just what I ordered. Arived timely.

    Related Items

    Customers Also Bought

    Sign-up for Exclusive Email offers 
    How to Order Track Your Package Shipping Returns Contact Us Customer Service Retail Store
    Getting Started Learning Center FAQ Dealers Customer Testimonials Affiliate Program
    About Us INSTEON Press Awards Employment Guarantees Security & Privacy
    Free Catalog Email Newsletter Forum RSS Site Map
    Have questions? Call us at 800-762-7846 (Mon-Fri 5am-7pm and Sat 6am-3pm PT) or send us a message
    Place your order by 3pm PT for same day shipping
    Copyright 1995-2014 SMARTHOME™
    Verisign Secure Site PayPal Acceptance Mark