CAS

Revision as of 09:53, 8 August 2013

Channel Associated Signaling is a signaling protocol for the set-up and tear-down of phone calls. It is different from other signaling protocols such as SS7 in that it is not message/packet-based but rather based on bit transition for state changing, and tone transmission for information and state information exchange. In many parts of the world, CAS was first replaced by ISDN and in many cases, was ultimately replaced by SS7. Today, CAS is often used with low density trunks.

CAS and TelcoBridges

CAS signaling is supported at the basic API level but is not supported at the Toolpack / Web Portal level and is thus not accessible for more basic applications (i.e., that don`t require programming code). As of June 2010, support for CAS R2 has been announced within the Toolpack Web Portal v2.5; this is slated to ship during the 3rd quarter of 2010. Please note that CAS R2 support is limited to E1 interfaces. It is not compatible with DS-3 or STM-1 interfaces.

CAS

CAS R1

Support for CAS R1 has been introduced in Toolpack release 2.7.42.

Please refer to Toolpack Web Portal v2.7.

Supported CAS R1 variants

The following CAS variants are currently supported by the Toolpack:

• E&M "Wink start" (delay start, 1 wink or 2 winks)
• FXS Loop start
• FXO Loop start

Please contact TelcoBridges regarding support for additional CAS variants.

Please refer to the following page for detailed information about [[CASr1_scripting|CASR1 script]

CAS R2

The TelcoBridges CAS R2 stack features a scriptable register signaling engine that, in practice, allows the complete customization of communication processes using tones. More specifically, it is possible to modify the timing(s) of the tone exchanges, change the meaning(s) of each tone and dynamically specify the sequence in which the tones are played. The CAS R2 stack also provides integrated interoperability between variants and between other signaling types. For instance, the calling party category can be converted between variants and propagated to a SS7 call leg.

Supported CAS R2 variants

The following CAS variants are currently supported by the Toolpack:

• Generic (ITU spec base)
• Brazil
• Mexico

Using Toolpack's script-based approach to the management of regional variants, variants supplied Toolpack can be adapted to address specific requirements and new variant scripts can be created from scratch, without to need to 'patch' or update the underlying system software version.

References

• CAS R2 Scripting guide
• CAS R2 Troubleshooting guide
• Wikipedia article
• ITU Q.400-Q.490 Specification