HUNTSVILLE, Ala.--(BUSINESS WIRE)--ADTRAN®, Inc., (NASDAQ:ADTN), today announced it is strengthening its market-leading VoIP switch portfolio with the addition of the NetVanta 1510 and 1550 families of Gigabit Ethernet switches. Traditional switch vendors are building products without a focus on the demanding application needs of Voice over IP (VoIP). As a result, businesses are experiencing voice issues like dropped calls and inconsistent call quality. By expanding the best VoIP switch portfol