From Fiscal Year 1998 Audit Report
NTT (Nippon Telegraph & Telephone Co.) had gradually been replacing its old metallic telephone cables between NTT branch offices and distribution points (e.g. an entry point to an apartment building) with new optical ones. Because the electric signal is used between distribution points and subscribers telephone equipment, NTT has to install Remote Subscriber Modules (RSBMs), which convert electric and optical signals alternatively at the distribution points accordingly (see illustration). RSBMs accommodate "packages for telephone circuit"(PTCs), and each PTC can connect RSBM to only one analog telephone line.
NTT’s RSBM installation
Demand for NTT’s telephone lines
The number of NTT’s traditional telephone lines had been decreasing since 1992 (61.22 million lines at the end of 1992), because of the rapid dissemination of cellular phones, and of the drastic shift from analog telephone lines to ISDN (Integrated Services Digital Network) lines.
The Board examined 207,390 PTCs loaded in 1,199 RSBMs in 41 NTT branch offices (purchasing price ¥1,696 million). When the Board compared the estimated numbers of analog telephone lines to be connected to PTCs and the actual number of analog telephone lines in operation in the loading list, the Board found that the former was much larger than the latter. Because of this, the purchased PTCs (purchasing price ¥56 million) were not fully and effectively utilized.
Following the Board’s findings, the NTT-East and NTT-West (devided successors of NTT) issued an instruction document requesting the offices concerned to review the estimates during the connection work stage based on the latest demand figures so that the number of PTCs to be accommodated can be adjusted to the actual demand, or to use vacant PTCs, if there is no prospect of connection, for other RSBMs.
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