Channel-Associated Signaling

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Channel- linked signaling or Channel-Associated Signaling ( CAS ) describes signaling methods that do not have their own signaling channels. The signaling information required for a telephone call is also transmitted in the voice channel.

CAS signaling methods are relatively old, they were introduced at the beginning of the telephone. Today, CAS is only used on analog telephones. Today, instead of the method are common channel signaling (engl. Common-channel signaling ) is used in which separate channels are used for signaling information ( D-channel , Signaling System No. 7 ).

CAS signals using signals that can differ from the speech being transmitted at the same time, for example direct voltages , low-frequency vibrations below the voice band, frequencies above the voice band, special frequency mixtures that do not occur in speech, impulses .

In this way, for example, ringing signals ( ringing voltage ), dialed telephone numbers ( pulses , audio frequency mixtures ), charge pulses are transmitted . Because of the limited possibilities to generate signals, the signaling information with CAS is kept very simple, so that usually only connection establishment and termination can be controlled with it.

literature

  • Jacek Biala: Cellular and Intelligent Networks. 2nd revised edition, Friedrich Vieweg + Sohn Verlagsgesellschaft mbH, Braunschweig 1996, ISBN 978-3-322-87271-5 .
  • PR Gerke: New communication networks. Springer Verlag, Berlin / Heidelberg 1982, ISBN 978-3-642-93207-6 .
  • VS Bagad: Telecommunication Switching Systems and Networks. Technical Publications Pune, ISBN 978-8-1843-1590-5 .

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