CAMEL wasspecification alwayswere intended to be specifiedpublished in phases.,<ref name="Release 96 Spec">[http://www.3gpp.org/ftp/Specs/archive/02_series/02.78/0278-560.zip 3GPP TS 02.78] Release 96 specification for the service aspects of CAMEL Phase 1 & 2 (zip file).</ref> with four phases having been established {{Asas of|2007}}, there have been 4 phases specified, each building on the previous phase.<ref name="Release 5 Spec">[http://www.3gpp.org/ftp/Specs/archive/22_series/22.078/22078-5f0.zip 3GPP TS 22.078] Release 5 specification for CAMEL phase 4 (zip file).</ref> Phases 1 and 2 were defined before [[3G]] networks were specifiedexisted, and as such support adding IN services to a [[Global System for Mobile Communications|GSM]] network, although they are equally applicable to 2.5G and 3G networks. Phase 3 was defined for [[3GPP]] Releases 99 and 4, and hence is a GSM and [[Universal Mobile Telecommunications System|UMTS]] common specification, while Phase 4 was defined as part of 3GPP Release 5.
In line with other GSM specifications, later phases should be fully backwards compatible with earlier phases; this is achieved by means of the [[Transaction Capabilities Application Part]] (TCAP) Application Context (AC) negotiation procedure, with each CAMEL phase beingis allocated its own AC version.<ref name="CAP Release 5 Spec">[http://www.3gpp.org/ftp/Specs/archive/29_series/29.078/29078-590.zip 3GPP TS 29.078] CAMEL Application Part specification for Release 5 (zipped Word document).</ref>
===Phase 1===
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===Phase 2===
'''CAMEL''' Phase 2 enhanced the capabilities defined in Phase 1. In addition to supporting the facilities of Phase 1, Phase 2 included the following:
* Additional event detection points
* Interaction between a user and a service using announcements, voice prompting and information collection via in-band interaction or [[Unstructured Supplementary Service Data|Unstructured Supplementary Service Data (USSD)]] interaction
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===Phase 4===
The fourth phase of CAMEL built on the capabilities of phase 3. The following features were defined:
* CAMEL supportSupport for Optimal Routing of circuit-switched mobile-to-mobile calls
* The capability for the gsmSCF to create additional parties in an existing call (Call Party Handling)
* The capability for the gsmSCF to create a new call unrelated to any other existing call (Call Party Handling - new call)
