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).
Extract from a memo discussing open vs. closed magnetic circuits for induction coils.
| Identifier | ExFiles\Box 54\4\ Scan070 | |
| Date | 1st January 1931 | |
| X4654 Extract from memo in X.6058 ref. RL/M5.1.31. It is usually thought that open magnetic circuit is best for an induction coil used under our conditions, but we originally (and still) made hedgehog ends as invented by J. {Mr Johnson W.M.} Swinburne 30 or more years ago, but it may be that still nearer or actually a closed circuit, may be better. The wireless coils of Ferranti may suggest something but to make a series of experiements might be worth while to see if we could use less of the expensive fine secondary wire. R. {Sir Henry Royce} | ||