F1OPT或H1B老师联邦税是否可免?

今日研究中美税务条约,见第19条表述如下:

"ARTICLE 19
(Teachers, Professors and Researchers)
An individual who is, or immediately before visiting a Contracting State was, a resident of the other Contracting
State and is temporarily present in the first-mentioned Contracting State for the primary purpose of teaching, giving
lectures or conducting research at a university, college, school or other accredited educational institution or scientific
research institution in the first mentioned Contracting State shall be exempt from tax in the first mentioned
Contracting State for a period not exceeding three years in the aggregate in respect of remuneration for such
teaching, lectures or research."

此条例并无规定免联邦税须持何种签证。本人在F1OPT 和H1B其间均为教师,这是否意味着我可以免联邦税。可有人依此条例免过税，望能探讨分享经验。