New London — Imagine you are watching cable TV and a third of your channels suddenly disappear before your eyes.

That's what is about to happen to local Atlantic Broadband customers who haven't been heeding company warnings about new encryption technology going into effect in three waves starting Nov. 14. Without the new equipment now required for each TV set, all Atlantic Broadband channels are scheduled to be encrypted as of Dec. 12, meaning customers no longer will be able to access them.

But take heart. Customers who call the Atlantic Broadband hotline number, (888) 674-4898, can learn how to get the proper equipment to avoid such TV interruptions.

"You have to have a converter, that's the big change," said Charles P. "Chap" Hanley, vice president and general manager for the company in Connecticut, during a recent interview at Muddy Waters cafe.

Many of the devices already have been shipped to 17,000 customers with older converters, but some people with additional TVs may need to take action to ensure each of their sets will be able to get all available channels. An additional 3,000 customers currently without boxes also will need to get the new converters.

Atlantic Broadband's new converters are necessary for security reasons, Hanley said, and most other cable companies already have implemented encryption, building the cost into the monthly price. Encryption keeps noncustomers from stealing signals, he said, a problem particularly with more technologically advanced TV sets.

"We're trying to secure our network," Hanley said. "I'm trying to get it all done before Christmas."

Every Atlantic Broadband customer now will need the new converter boxes. Those who don't have them for each of their TVs will lose channels such as CNN starting Nov. 14, then will lose another one-third of their channels Dec. 5 and the final one-third (with many sports channels) Dec. 12.

He encouraged people to come in to the Atlantic Broadband offices at 61 Myrock Ave. in Waterford to pick up the equipment (office hours are being extended). Technicians will be able to help out for cable users who cannot make it in and for business customers, he said.

Two standard-definition converters will be given out free of charge for the first year; additional boxes will cost $2.99 a month each, as will the other converters in the second year. HD converters are a couple dollars more.

One benefit of the new converter box, Hanley said, is that the latest channel guide is much more complete, making it easier to plan TV viewing.

l.howard@theday.com