The International CAS package (icas) provides an extension to the Basic CAS packages, defining additional line signals and events required for international signalling protocols.

For some international protocols, such as some variants of the R2 Signalling System, it would typically be necessary to implement the bcas, icas and casblk packages to fully support the interface. In addition, register signalling will require support of either the bcasaddr package for non-compelled signalling, or a package to perform compelled signalling.