máy tính lớn đã được tìm thấy thiếu tính linh hoạt để hỗ trợ phát triển phần mềm ngày nay thời gian thực, năng động và môi trường xử lý. Giao dịch dựa trên Internet, ví dụ, thường sẽ đòi hỏi việc sử dụng các bộ vi xử lý độc lập nằm tại địa điểm mạng khác nhau. | Voice Network Access 155 high-availability or fault-tolerant platforms. Consequently systems with these features are often more expensive. Power protection. PBXs are software-driven systems. If power is interrupted all program processes in memory can be lost and require restart. This is particularly true with older PBX systems. Many come equipped with uninterruptible power supplies UPSs that typically have enough power to run or shutdown the system until the UPS battery supply is used up or a backup generator resumes power 1 . Some companies have back-up generation or dualutility feeds to maintain power. Some PBXs system vendors provide generators with their systems. Station failover. Many PBXs are equipped with the ability to automatically transfer certain stations directly to an access trunk or lines upon failure bypassing the PBX altogether. It is also wise to have a basic single-line phone connected to dedicated plain old telephone service POTS lines which do not go through the PBX as an extra backup. Remote switch modules. Organizations and call centers occupying large buildings often use PBXs that are partitioned into multiple switches situated at different locations in the building. This provides switch diversity and enables voice operation to continue in the event a portion of the building experiences a physical disaster or the system simply fails. A two-way trunk is established between the two modules to carry calls from one location to the other. Each module can also be homed to a different building entry point and even to a different carrier CO. Multihomed stations. Used typically in conjunction with multiple switch modules this strategy connects every other station to a different switch module regardless of where the station lies in the building. The purpose of this strategy is to keep each workgroup s operation partially functional in the event one switch module becomes inactive. This approach can result in a cabling nightmare and be expensive to .
