This means that voice signals travel on the same circuits as line status, address, and alerting signals. As there are 24 channels on a full T1 line, CAS interleaves signaling packets within voice packets, and therefore, there are a full 24 channels to use for voice. Various types of CAS signaling are available in the T1 world. The biggest disadvantage of CAS signaling is that the network uses bits from information IP packets, such as voice packets, to perform signaling functions. CAS is not the optimal choice when trying to achieve the highest possible connection rates with modems.
Most modems can adjust to the signal quality and still give high-speed reliable connections.
However, the use of 56K modems on CAS lines will drop the connection speeds by almost 2K in the downstream direction of communication, per trunk that uses CAS signaling. Before you can configure your Cisco router to use VoIP, it is best if you understand the concepts of QoS features in Cisco IOS software. Cisco Systems Inc. All rights reserved. Important Notices and Privacy Statement .