From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Photograph of portable electronic testing equipment in a carrying case, connected to a separate microphone or speaker component.
| Identifier | ExFiles\Box 138\1\ scan0220 | |
| Date | 7th January 1936 guessed | |
| 5. MS.352.19 EICHTASTE H.B. GEN. A.B. JUST. +40 +20 +0 -20 -40 +70 -10 -60 PHON | ||