Conventional wisdom holds PSTN trumps VoIP when it comes to over-all quality, but the gap is closing, according to a study from Keynote Competitive Research of San Mateo, Calif. The study compared the PSTN (public switched telephone network), PacketCable and VoIP hard phone services in the New York and San Francisco markets from June 1-30.

Voice services from AT&T's CallVantage [1] and PSTN service; Comcast, Primus Lingo [2], Packet8, SunRocket (before it died [3]), Time Warner Cable, EarthLink [4], Verizon's VoiceWing [5] and PSTN; Vonage [6] and Vonics Digital were evaluated for audio clarity, and reliability during peak and off-peak times.

Keynote placed 125,000 calls to make the assessment. While only two of the eight services tested provided 100 percent "availability" in the tests, VoIP nonetheless was deemed "highly competitive" with traditional PSTN. The most obvious factor not mentioned by Keynote would be price.

For More:
- Keynote's summary is here [7] 

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