Homeowners who make their phone calls with Voice over Internet Protocol (VoIP) telephone services may want to check their security alarm systems, warns a Winnipeg man who recently found out his house had not beenproperly protected for over a year.

Dennis Terrick said he had no idea the VOIP phone service he signed up for 18 months ago was incompatible with his home security system. He learned his alarm signal was not being received by the security company, meaning any calls for help would have gone unanswered.

"I had been in this comfort zone of knowing that my house was patrolled for a year and a half when in fact it hadn't been," Terrick told CBC News on Thursday.

"I was really disturbed … while nothing did happen in the year and a half, so that was comforting, but I don't like to operate that way."

VoIP uses a high-speed internet connection as a phone line instead of a regular analog line — and often at a fraction of the cost of traditional land-line phone services.

Terrick said no one at Primus, his VoIP provider, told him about incompatibility issues with security systems when he signed up for the service.

Primus spokesman Dmytro Marushkevych said that kind of information is available to customers, but it's buried within a lengthy contract.

"We never had major issues with that," he said, saying he had received few customer complaints.

"If [a] customer has some other services, some other ways that they're using their phone system for something else, then it's [the] onus on the customer to see, or ask us, 'what about our security system?'"

Problems reported

But David Currie with the Canadian Security Association said companies are hearing of problems. Currie, who owns a Sarnia, Ont., security alarm firm, said 25 of his customers have found their alarms do not work once they switch to VoIP telephone service.

The incompatibility between VOIP and alarm systems can arise because almost 90 per cent residential alarm systems operate on conventional phone lines, he said.

"When you try and marry that kind of equipment to the newer technology, there's many problems that arise there. Some days it will work, other days it may not work," he said.

"If a customer is going to change their phone service to VoIP, I would strongly urge them to consider changing their alarm communications to internet or cellular reporting directly."

But Terrick said he is taking another route — switching back to a traditional land-line for his telephone service.