Manufacturers DT Services specializes in telecom equipment consignment and the resale of used business phones. View some of our manufacturers below! Aastra Adtran Allworx Altigen AT&T Avaya Cisco Comdial ESI Hitachi Inter-Tel Iwatsu-Omega Lucent Mitel NEC Nitsuko Nortel Panasonic Plantonics Polycom Samsung Shoretel Tadiran Telrad Toshiba Vodavi