Section 874.1925 - Toynbee diagnostic tube(a)Identification. The toynbee diagnostic tube is a listening device intended to determine the degree of openness of the eustachian tube.(b)Classification. Class I (general controls). The device is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to § 874.9 .51 FR 40389, Nov. 6, 1986, as amended at 65 FR 2316, Jan. 14, 2000