Window Bugs are sensors you can mount on your windows to trigger your alarm system upon the breaking of glass. However, since they require your alarm panel or system to be a fast-acting initiating circuit, with a response time of 20 milliseconds or faster, some systems may not detect the brief broken loop time. The Pulse Stretcher can be used with one or more units to provide a longer pulse when required, guaranteeing that your alarm system will know that an intruder is trying to get into your home. Window Bugs and alarm systems are sold separately. The Pulse Stretcher will accept an unlimited number of Window Bugs. It automatically resets the loop circuit upon completion of the alert. Be sure to test the Pulse Stretcher at least once a year.