Cell phone coverage in Chilmark and Aquinnah will get a boost, this time for Verizon customers, after the major carrier signed on to use the digital antenna system (DAS) in the up-Island towns.

Chilmark executive secretary Tim Carroll said on Wednesday that testing is in its final stages, and that full Verizon Wireless service could be available as soon as June 1 or July 1 at the latest. AT&T signed on to the DAS system as a carrier last year.

Before the DAS system was completed last year, cell phone coverage was spotty at best and mostly unavailable in Chilmark and Aquinnah. Once the towns found agreement on how to provide cell phone coverage, they contracted with the American Tower Company to build the DAS system.

The system uses antennas attached to existing telephone poles. Both Verizon Wireless and AT&T are connected to 15 antennas across Chilmark and Aquinnah; there are also three new antennas for Verizon Wireless in Chilmark, one near Blue Barque Road and two on North Road, Mr. Carroll said.

American Tower notified selectmen in the two towns of the Verizon Wireless agreement in a letter earlier this month.

“The additional antenna locations will expand the coverage footprint to reach an even broader area than the system currently provides for,” American Tower area vice president Jeffrey Baker wrote in a May 2 letter.

Final testing is under way for the enhanced 911 system, which enables emergency responders to locate the position of a mobile caller, Mr. Carroll said. He said the emergency call system needs to work properly before Verizon Wireless can join the system.