Call Progress Analysis

Overview:

Telephony applications on POTS networks require the ability to accurately and rapidly detect and classify the call progress tones, such as dial tone, ring-back and busy, that are sent by the network to the calling equipment. These tones are usually composed by one or two sinusoidal components with specified frequencies and on/off temporal patterns (steady tones or tones with on/off cadences).

The specifications for call progress tones are defined by a Precise Tone Plan. Unfortunately there is no worldwide standard for it and these make the Call Progress Analysis (CPA) more complicated. Therefore it is desirable for a CPA algorithm to be able to deal with all the various standard tone plans and still ensure a fast and reliable detection in all the real-world signal and noise conditions.

ASDSP's Call Progress Analysis (CPA) is based on single and dual tone detection by overlapped Goertzel FFT with optimally designed windowing and a state-machine based temporal pattern (timing) analysis; the timing can be either steady or cadence. So our CPA can recognize four type of call progress tones:

• Single continuous tones (a simple pure tone)
• Dual continuous tones (like a dialtone)
• Single tones with cadence (including the SIT tones)
• Dual tones with cadence

The frequency and timing parameters can be configured runtime through an INI file containing a set of parameters for each progress tone defined in the Precise Tone Plan.

Features:

• Run-time configurable to be compliant with every Precise Tone Plan
• Fast and reliable detection even with strong background noise
• Nexperia Processors supported: PNX1500, PNX1700, PNX0190, and PNX9520 processor families.

Technical Specs:

• Sampling rate 8 kHz
• Frame size 10 ms (scalable)

Application Areas:

• POTS Speakerphones
• Videoconference endpoints
• VoIP Gateways
• Automatic answering system, PBX
• Audio conference bridges

Other ASDSP Products from MDS: ASDSP Summary