DID Trunks Via the Cellular System

Abstract

Wired telephone trunks for Private Branch Exchange (PBX ) operation are often in short supply or lacking altogether in developing nation telephone systems. Even large businesses must often settle for individual lines which must be answered by an attendant and transferred to the called party. Congestion on these lines is also a problem in addition to their cumbersome operation. Cellular infrastructure can be installed in a short period of time to provide sufficient capacity and dependable call completion for many individual users, but heretofore the cellular system had nothing to offer business users who needed trunks to connect to their PBX.

BellSouth has conceived a service which permits true trunked operation via cellular and other interconnected wireless systems. The cellular system provides the transport from the Mobile Telephone Switching Office (MTSO) to the business site. This service is connected to the trunk side of the PBX, which reacts exactly as it would if it were connected to a wireline trunk. Operation is virtually transparent to parties on either end of the call, providing both Direct Inward Dialing (DID) and Direct Outward Dialing (DOD). One can appreciate that since no wired connection is required, this service can be installed very rapidly. It also affords the business user immediate portability with no number change if the business remains within the same cellular system.

BellSouth has staged a three month trial of this system in Latin America. Acceptance has been quite favorable. Users have commented positively on both the improved percentage of call completion and call audio quality. Some trial participants had wireline trunks connected to their PBX, and the trial simply added to their capacity. Other participants had no trunks and installed PBXs to trial the new technology. Not only will this technology increase cellular revenues, it will stimulate the PBX market which often languishes because there are few trunks available in specific telephone markets.