市內電話交換機經濟擴充週期之探討

Abstract

「經濟擴充週期」係指相隔多少時間擴充一次使得整個工程投資最為 經濟。市內交換機建設數量與金額龐大，需要以更精確的模式與方法求其 經濟擴充週期。本研究運用既有會計報表及相關資訊整理成建設成本資料 經由統計之虛擬變數迴歸分析，求得建設成本與建設門號數之迴歸方程式 ，再求解建設總成本現值之最小值其時間間隔的解即經濟擴充週期。 計算經濟擴充週期之方法以能使得整個工程投資總成本現值最小為原則。 本研究提供近似值法、牛頓法與逐月比較法三種方法計算經濟擴充週期與 建設總成本現值，研究結果發現在交換機有最大門號容量限制時以逐月比 較法最佳；在交換機無最大容量限制時以牛頓法最佳。 本研究希望能 協助市話交換規劃工程師迅速正確地擬訂各交換局最佳且最符合經濟利益 的可行擴充計畫，並協助計畫擬定者、預算編列者與設計者精確地計算出 每一擴充計畫之成本與預算。就理想與實務做進一步的探討﹐其理論與方 法提供參考，期能使市內交換機建設總成本現值為最小﹐以開源節流為電 信事業開創更輝煌的明天。 The Economical Expansion Interval（EEI）means time interval for which local telephone exchange expansion can achieve a minimum cost. Obtaining EEI is important for cost saving. In this empirical study, we analyze the data in accounting reports by using regression with dummy variables to get cost information, based on which EEI can be obtained. The methods for computing EEI are designed in such a way that present value of total cost is minimized. Three methods are discussed in this study. They are approximate value method, Newton's method and month-by-month comparison method. The results indicate that, when the maximum capacity of switching units are finite, the month-by-month comparison method is the best one; on the other hand, when the maximum capacity of switching units are infinite, Newton's method is our choice. The contribution of this study is that the research results can help plant extension engineers determine EEI to improve operational performance for the Northern Taiwan Business Group of Changhwa Telecom. Moreover, the approach proposed can be applied in similar relevant studies.