R.R.T.

1.
registered respiratory therapist.

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Rs
noun, plural R’s or Rs, r’s or rs. 1. the 18th letter of the English alphabet, a consonant. 2. any spoken sound represented by the letter R or r, as in ran, carrot, or rhyme. 3. something having the shape of R . 4. a written or printed representation of the letter R or r. […]
R.s.
1. right side. 1. Recording Secretary. 2. Reformed Spelling. 3. Revised Statutes. 4. Royal Society. R.S. Revised Statutes
Rs-232
EIA-232

Rs-232c
Renamed EIA-232C (2004-08-02)
Rs-232d
communications, standard The EIA equivalent of ITU-T standard V.28. [Difference from EIA-232/EIA-232C?] (1995-03-02)