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  CommServ > Reference > Background > PBX vs.Centrex: UC Berkeley

PBX vs.Centrex: UC Berkeley

The following are notes from a presentation made by a University of California, Berkeley, representative to the members of the UCSB Telephone Advisory Committee on December 1, 1995. The topic of the presentation was a comparison between Centrex telephone service and a campus-owned PBX (Private Branch eXchange) telephone switch.


  • U.C. Berkeley (UCB) has been using a PacBell Centrex service since 1985.
  • Their initial contract (in 1985) was renewed for another seven (7) years in 1992.
  • They have approximately 16,000 telephone lines on their system, including 3,000 for housing residents.
  • They intend to stay with Centrex at least until the end of their current contract (1999) and have no plans (yet) to change to a PBX after the contract expires.

Strengths & Weaknesses

Centrex Strengths

  • There was no capital expense. They estimated that it would cost $20 million to buy and install a PBX in 1992. Signing a contract for Centrex negated the need to borrow this amount of money.
  • They believe that Centrex provides the highest level of system survivability during and after an earthquake.
  • They want to keep their staff to a minimum and not have to hire technicians to provide installations and repairs.
  • They have some off-campus buildings that they wanted to integrate with their on-campus telephone system and felt that Centrex was the best way to meet this need.
  • Because of the size of their contract (16,000 lines), they are essentially the sole customer of the Nortel DMS-100 switch that PacBell uses to provide the campus with Centrex. This gives the campus great leverage to have PacBell make changes for the campus, usually at little or no cost. System software upgrades to the DMS-100 system are provided to UCB at no charge.
  • They receive 24 hour per day, 7 day per week maintenance without having their own staff of technicians.

Centrex Weaknesses

  • The University lacks control over the system.
  • It's difficult to get PacBell to provide specialized services, such as customized ISDN.
  • The Centrex provides current technology, but not leading edge technology. It will probably always be behind the leading edge of the industry.
  • It is very difficult to integrate their VoiceMail system with the Centrex system.




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