We have had a loss of phone service a few times, but my security system didn't detect that something was wrong. All security systems detect the dc voltage on the line, and when this voltage disappears, the security system knows that something is wrong. However, when we lost phone service, the modem still sent out the dc voltage on the in-house phone line, which goes through the security system. This a major flaw with this system and my security is compromised. How can this be rectified?