The No. 4 toll crossbar switching system is presently the backbone of the Direct Distance Dialing (ddd) network. Conversion of No. 4 offices equipped with the Electronic Translator System (ets) is vital to the rapid introduction of ccis to the ddd network. ccis capability represents a major increase in the role of the ETS software in the call switching process. Significant changes and additions to the switching equipment are required to support this expanded software control.
Current concepts in computer telecommunication are surveyed.Error detection with retransmisslon is shown to be the best method in general to achieve near error-free data transmission over common carrier channels. A new version is proposed by the authors which is specifically designed for fullduplex links. The superiority of this technique is demonstrated by a simulation program which compares the proposed partial retransmission scheme with an ideal block retransmission method with degraded line conditions.
Common‐channel interoffice signaling (ccis) represents a major advance in interoffice signaling speed and capability over current inband signaling systems. The introduction of ccis between Stored Program Control (spc) switching offices is reducing ineffective machine attempts (imas) caused by transmission and switching irregularities associated with inband signaling. Because signaling between ccis‐equipped switching offices is concentrated in a relatively small number of signaling links and signal transfer points (stps), a high standard of performance for the signaling network is essential. Therefore, the design of the signaling network incorporates many features to assure a high degree of availability. Cumulative data on stps and studies of signaling links are the principal measures of signaling network performance. Data on their performance are presented that confirm the high availability of the signaling network.
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