Davenport-headquartered security company Per Mar Security Service has acquired GT Fire and Security of Grand Island, Neb. Terms of the deal were not disclosed.The Nebraska company will be merged with Per Mar’s Midwest Alarm Services business, Per Mar said in a statement on its website.Sixty-seven-year old Per Mar reports more than 2,300 employees in 40 branches, including offices in Cedar Rapids.In November, it purchased NECO Security of Lincoln, Neb., and merged that company, too, with its Midwest Alarms business.