CAS Detection

There are three aspects to defining CAS detection performance: Signal recognition, Talkdown performance and Talkoff performance.
1) CAS recognition establishes the ability of the CPE to detect the CAS over the range of expected signal parameters in the absence of speech or noise.
2) CAS talkdown performance establishes the ability of the CAS detector to detect CAS in the presence of speech, music, and noise. The ability to detect CAS in the presence of interfering signals is necessary for proper operation with CIDCW. Although the far-end will be muted during transmission of the CAS, near-end signals may potentially corrupt the CAS and impede its detection.
3) CAS talkoff performance establishes the ability of the CPE to resist CAS imitations produced by speech, music, and noise. Distinguishing between legitimate CAS and those simulated by interfering signals is important for services like CIDCW. Falsely detecting a CAS simulated by interfering signals will result in undesirable breaks in the Voicepath, which will adversely affect telephone service quality. Robust CAS performance is necessary because a CAS detector constantly monitors the line and is exposed to both near-end and far-end signals.