11. Trunk lines are used for connecting a private branch exchange ( PBX ) to a telephone service provider. 12. SIPfoundry spawned the development of sipX, an open source SIP private branch exchange ( PBX ) for Linux. 13. Such systems may be supported by a private branch exchange ( PBX ) which controls internal communications between telephone extensions. 14. ISDN signaling is used primarily on trunks connecting end-user private branch exchange ( PBX ) systems to a central office. 15. Business telephone systems are often broadly classified into key telephone systems, and private branch exchanges , but many hybrid systems exist. 16. The system would be inserted into the widely used communications routing technology known as the PBX, or private branch exchange . 17. GPT has 30 percent of the U . K . private branch exchange market, while Siemens's Hicom product has 5 percent. 18. Mercury moved into the Private Branch eXchange market in 1990 as a result of Telephone Rentals being bought by Cable & Wireless. 19. The system relies on the PBX _ or private branch exchange _ telecommunications routing technology that is already common in call centers. 20. "' Vertical Communications, Inc . "'is a corporation that specializes in premises-based private branch exchanges , i . e ., business telephone systems.
