Most modern security alarm systems have the ability to detect a dial tone when sending a signal to the monitoring station. If a dial tone is not detected, the panel assumes there is a call on the line so it hangs up and tries again.
This feature, although very handy when it comes to preventing transmissions from being jammed, has a draw-back. Some Panels see the intermittent Voice mail indication dial tone as no dial tone. If this is the case, your security alarm system will not be able to send a signal to the monitoring station.
If left untreated, this problem could result in a very dangerous situation. Fortunately, most alarm manufacturers have a programming fix. The programming feature is called Dial tone detect disable or Force dial of no dial tone. Proper programming of this feature will repair the problem. Depending on your phone company and your voice mail settings, you may also be able to change this indication. Some phone companies will give an intermittent tone for about 3 seconds then switch to a steady tone. This should not cause a problem with your security alarm system.
To determine if your security system needs re-programming, a simple test is to leave yourself a voice mail message then trip your alarm (Ensure the monitoring station knows you will be testing your security alarm system.) Keep in mind, some companies, like ADT has standard abort delays, which will not send a signal to the monitoring station if the siren only rings for a few seconds. This is great for eliminating false alarms, unfortunately it also leaves time for the criminal to disable the system.