Hearing aids are automatically checked by circuit that applies half-second test signal every thirty minutes. If hearing-aid output is distorted, too small, or if battery is too low, a warning lamp is activated. Test circuit is incorporated directly into hearing-aid package.
Hearing-aid tester
NASA Tech Briefs ; 2 , 3
1977-11-01
Miscellaneous
No indication
English
Dynamic friction tester ( DF Tester )
Automotive engineering | 1992
|Engineering Index Backfile | 1945
|Engineering Index Backfile | 1945
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