In case Tabot is unwilling to testify on our behalf, perhaps he would allow us to use the following explanation from his patent 7248125.

<A convention ring oscillator is typically employed as a VCO for CMOS technology. The conventional ring oscillator consists of a string of inverters having their supply controlled by a control voltage. The conventional ring oscillator requires an odd number of inverters that provides an odd number of phases. >

http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=7248125.PN.&OS=PN/7248125&RS=PN/7248125

Opty