| 摘要 |
<p>PURPOSE:To enable a simple facility to select either loop transmission line, by sending office frequencies of two supervised offices at far-end sides to a supervisory office in a direction that one section each is overlapped. CONSTITUTION:Supervisory office S, and supervised offices A1 to A7 are connected in a loop as shown in the figure. Two supervised offices A3 and A4 at far-end sides send out office signals (f3) and (f4) to supervisory office S closkwise and counter- clockwise respectively. Supervisory office S allows receivers D3 and to D4 to receive those office signals to detect the fault of the transmission line. Namely, it can be detected that one of sections (1) to (3) when only signal (f4) can not be received, one of sections (5) to (8) when only signal (f3) can not be received, or section (4) when neither signal can be received gets out of order. Consequently, supervisory office S can communicate with a supervised office using a transmission line without fault.</p> |
