Alarm Systems may not work with digital telephone service.

Digital telephone service -Voice Over Internet Protocol, or VoIP, uses the internet to transmit telephone calls. Instead of the standard telephone lines that run from our homes and business to the local telephone switching office, VoIP uses a special DSL telephone line, a cable TV coaxial cable, or a wide area wireless connection. Low prices, particularly for long distance calls,  make this an attractive alternative to the old telephone companies. But these savings may cost you more than you expect.

Alarm systems have used standard business and residential telephone lines to transmit information and alarms to authorities for decades. They work much like the modem on a computer. And VoIP capable alarm system transmitters are entering the market now. But the vast majority of the millions of alarm systems in use today use POTS, Plain Old Telephone Service, to transmit signals to the Central Monitoring Station which then notifies the authorities that an alarm condition exists.

Several potential problems arise when switching to VoIP. The first has to do with electrical power. Telephone companies generate telephone line power at the local switching station. So during a power failure your telephones will likely still operate. Some telephones are powered by a small transformer which operates special features. These telephones may not ring, and you may not be able to dial out, but the telephone line itself will usually still work during a power outage. This is all that is required for an alarm system to communicate with the central monitoring station. The VoIP system requires a modem powered by the home or business electrical supply. If the power is off due to storm, provider failure, or intentional act, the modem will not operate and telephone service is interupted, thereby rendering the alarm system incapable of communicating with the central station. Additionally, if your internet service provider has a server or other failure, your telephone service will be interupted along with your internet service.

The second potential problem with switching to VoIP telephone service has to do with the format of the
transmitted alarm information. We have seen several newer model alarm systems transmit over VoIP with no apparent problem. However, we have discovered that a number of older models will not transmit, or will transmit garbled information to the central monitoring station. Reprogramming the alarm control to change the transmission format may resolve this issue.

The third potential problem lies in the actual work done to change to VoIP. Alarm systems are wired to the home or business telephone lines in a way that allows the alarm to take control of the line when it needs to communicate. You may have learned that if a phone is off the hook in one room, and you try to use a phone in another room, you get no dial tone, or are unable to dial. Line seizure allows the alarm system to dial if a phone is in use, or just off the hook. If the VoIP installation changes this wiring configuration, alarm communication may be disrupted.

If you switch to VoIP you should consider keeping one standard telephone line for your alarm system. One large digital telephone service provider, on its website, recommends doing so. This may require a visit by your alarm company service technician (and the resultant fee) to test and reconfigure the wiring to the alarm control panel after the installation of VoIP.

A cellular or radio alarm reporting system may be an economical means of assuring alarm transmission. This is recommended (and required in some high-security locations such as banks) even with standard telephone service.  

To prevent a local or wide area power outage from affecting alarm transmission, install a back up power supply for the modem. You can use a Universal Power Supply (UPS), or a generator. But it must  generate power long enough to outlast a power failure. This can be very costly.

Expect to spend a little money with your alarm company if you switch to digital telephone service. A visit by a technician for complete system testing after VoIP installation will go a long way to providing peace of mind. And you can still save money on a phone call to that old friend or relative on the other side of the world.