Intel® Dialogic® analog call technology uses a method of signal identification for call analysis that can also detect fax machines and answering machines.
Call analysis is initiated when a call is dialed. Call parameters are determined by the parameters and values defined in the voice DX_CAP call analysis parameter data structure. On Springware boards, the default parameter values defined in the DX_CAP data structure can be changed by the gc_LoadDxParm( ) function to fit the needs of your application. (The default values cannot be changed on DM3 boards.) For a detailed description of enhanced call analysis (PerfectCall) and how to use call analysis, see the Voice API Programming Guide.
For each analog call, signaling information is sent to the local CO and then to each successive CO until the destination CO is reached. The destination CO attempts to connect to the called party. Concurrently, the destination CO sends back signaling information representing the condition or status of the called party`s line. This signaling information passes through the network as audio tones. The number of tones used and the frequency combinations used to convey this signaling information vary from country to country. Also, whenever a call is switched via networks that do not support or pass caller identification information, then this information can be lost.
The following sections describes analog signaling as it is used in a network, DTMF (dual tone multi-frequency) signaling, global tone detection considerations, and the Global Call call analysis capability. See also Section 5.3.2. Country Dependent Parameter (.cdp) Files for using call progress tones to determine the condition of a call.
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