> For the complete documentation index, see [llms.txt](https://prosbcdocs.telcobridges.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://prosbcdocs.telcobridges.com/telecom-references/ss7-and-signalling/cas.md).
# CAS
Channel associated signalling (CAS): how call setup and teardown signalling rides with the voice channel, the R1 and R2 variants supported, and the E1/T1/J1-only limitation.
> **Applies to:** Tmedia 2.7, 2.8, 2.9, 2.10, 3.0, 3.2, 3.3
Channel Associated Signaling (CAS) is a signaling protocol for the set up and tear down of phone calls. It is different from other signaling protocols, such as [SS7](/telecom-references/ss7-and-signalling/ss7.md) because it is not message or 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](/telecom-references/ss7-and-signalling/isdn.md), and in many cases, was ultimately replaced by SS7. Today, CAS is often used with low-density trunks.
### CAS and TelcoBridges
TelcoBridges provides support for various CAS R1 and CAS R2 variants. Please contact TelcoBridges regarding support for additional CAS variants.
**Note:** CAS support is limited to E1/T1/J1 interfaces. It is not compatible with DS-3 or STM-1 interfaces.
### CAS R1
Toolpack supports various CASR1 variants on T1 and E1 line interfaces.
The TelcoBridges CAS R1 stack features a scriptable register signaling engine that allows the complete customization of CAS R1 variants and call flows, including the creation of new variants that are not provided with Toolpack.
Refer to [CASR1 script](/telecom-references/ss7-and-signalling/cas/casr1-scripting.md) for detailed information.
**Note:** Support for CAS R1 has been introduced in Toolpack release 2.7.42.
#### Supported CAS R1 variants
The following CAS variants are currently supported by Toolpack:
| CASR1 Variant | RELEASE |
| ------------------------------------------------------------------------------------------------- | ------- |
| E\&M "Wink start" (delay start, 1 wink or 2 winks) | 2.7 |
| [Loop start user side](/telecom-references/ss7-and-signalling/cas/cas-r1-loopstart-user.md) | 2.7 |
| [Loop start network side](/telecom-references/ss7-and-signalling/cas/cas-r1-loopstart-network.md) | 2.7 |
| Ground start user side | 2.8 |
| Ground start network side | 2.8 |
### CAS R2
Toolpack supports various CASR2 variants E1 line interfaces.
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.
**Note:** Support for CAS R2 was introduced in Toolpack release 2.5.
#### Supported CAS R2 variants
The following CAS variants are currently supported by Toolpack:
| CASR1 Variant | RELEASE |
| ----------------------- | ------- |
| Generic (ITU spec base) | 2.5 |
| Brazil | 2.5 |
| Mexico | 2.5 |
| Venezuela | 2.7 |
Use Toolpack's script-based approach to the management of regional variants. Variants supplied by 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.
### H.248 and CAS
Starting with version 2.8, CAS support for H.248 has been added. This means TDM CAS lines can be controlled remotely through H.248 CAS messages. Supported packages are described in the [H.248 page](/telecom-references/sip-and-voip/h248-mgcp.md#h248-package-support).
### Configuration
* [Web Portal v3.2, v3.3: CAS Signaling](https://prosbcdocs.telcobridges.com/tmedia-documentation/configuration/web-portal-previous/web-portal-3-2/protocol-stack/protocol-stack-settings#cas)
* [Web Portal v3.0: CAS Signaling](https://prosbcdocs.telcobridges.com/tmedia-documentation/other-pages/protocol-stacks-general/tmedia-tdev-and-tsig-web-portal-3-0-protocol-stacks#cas)
Click here for other versions
* [Web Portal v2.10: CAS Signaling](https://prosbcdocs.telcobridges.com/tmedia-documentation/configuration/web-portal-previous/web-portal-2-10/tmedia-tdev-and-tsig-web-portal-2-10-protocol-stacks#cas)
* [Web Portal v2.9: CAS Signaling](https://prosbcdocs.telcobridges.com/tmedia-documentation/configuration/web-portal-previous/web-portal-2-9/web-portal-2-9-protocol-stacks#cas)
* Web Portal v2.8 and earlier: documentation is no longer published. Contact [technical support](https://prosbcdocs.telcobridges.com/tmedia-documentation/operations-and-support/support/contacting-telcobridges-technical-support) if you need it.
### References
* CAS Scripting
* [CAS R1 Scripting guide](/telecom-references/ss7-and-signalling/cas/casr1-scripting.md)
* [CAS R2 Scripting guide](/telecom-references/ss7-and-signalling/cas/cas-r2-scripting.md)
* [CAS R2 Troubleshooting guide](https://prosbcdocs.telcobridges.com/tmedia-documentation/operations-and-support/troubleshooting/how-to/toolpack-cas-r2-troubleshooting)
* [H.248](/telecom-references/sip-and-voip/h248-mgcp.md)
* [Wikipedia article](http://en.wikipedia.org/wiki/Channel_Associated_Signaling)
* [ITU Q.400-Q.490 Specification](http://www.itu.int/rec/T-REC-Q.400-Q.490-198811-I)
## In this section
* [CAS R1 E\&M](/telecom-references/ss7-and-signalling/cas/cas-r1-e-and-m.md)
* [CAS R1 LOOPSTART NETWORK](/telecom-references/ss7-and-signalling/cas/cas-r1-loopstart-network.md)
* [CAS R1 LOOPSTART USER](/telecom-references/ss7-and-signalling/cas/cas-r1-loopstart-user.md)
* [CAS R2 BACK DIGITS](/telecom-references/ss7-and-signalling/cas/cas-r2-back-digits.md)
* [CAS R2 scripting](/telecom-references/ss7-and-signalling/cas/cas-r2-scripting.md)
* [CASr1 scripting](/telecom-references/ss7-and-signalling/cas/casr1-scripting.md)
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