cymoscope

• cymatoscope (philologically prescribed, but sees little actual use)
• kumascope

First attested as cymatoscope in 1903 and as cymoscope in 1905; formed as cȳm- (the short stem of the Latin cȳma, from the Ancient Greek κῦμα (kûma), kūma, “wave”) + -o- +‎ -scope. Cymatoscope is philologically prescribed in place of cymoscope because it preserves the long stem (κῡμᾰτ- (kūmat-), kūmat-) of its ultimate Ancient Greek etymon, which properly does not form compounds on its short stem (κῡμ- (kūm-), kūm-).

• (Received Pronunciation) enPR: sīʹməskōp, IPA^(key): /ˈsaɪməskəʊp/

cymoscope (plural cymoscopes)

1. (wireless telegraphy, disused) A detector of electromagnetic waves.
   • 1905, Engineering, LXXIX, page 742:

     Apparatus belonging to any of these groups might all be called a cymoscope, or wave-detector.

• “cymoscope” listed in the Oxford English Dictionary [2nd ed., 1989]