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designation, would have been terrestrial with no TASI or DCME, and the C6 signalling on the data link could perform for 48 or 96 traffic channels. It could function for up to 2,048 in the maximum. The question is whether two operators would have that many traffic channels between them, dependent on
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were slowly beginning to exceed these data rates over 4w circuits; these data links had the advantage that there was no national tail from the ISC out to a normal end point in the country. It was often the
National Section that detracted the most from the quality and reliability of such links.
186:. Taking the signalling function away from the traffic channel could cut costs, and would later lead to Common Channel Signalling. There would be no need for filtering signalling away from speech, and the duty cycle of the costly trunk for each revenue earning call would be better. Signalling
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Finally it was considered possible that a mesh of such data channels could be set up between major centres, leading to a system where the link between country A and country B could perform the signalling functions for links to country A from country D for example.
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just one bearer for signalling and subject to occasional failure. It was of course practice to have standby route over a diverse path in case of outage on the original DP data circuit link.
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telephone calls. The next development was correspondent and non-correspondent switching of telephone calls by new operators in the countries where more sophisticated methods were required.
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CCITT No 6 was a method developed & implemented by administrations in a limited number of countries for use in correspondent
International Switching of
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would be significantly shorter than with C4 and C5. With telephone signalling not transmitted over the line, the opportunities for
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between international switching centers (ISCs). It is specified in
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178:(DCME). These transmission methods were not suited to
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46:. Unsourced material may be challenged and removed.
154:or electronically controlled cross-points such as
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275:- Specifications of Signalling System No. 6
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96:January 2011
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192:clear down
174:(TASI) or
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