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).
Specifications for the coils used in an auto switch.
| Identifier | ExFiles\Box 59\1\ Scan173 | |
| Date | 11th November 1927 | |
| To HY{Tom Haldenby - Plant Engineer}/RD. from EFC. X 4008 EFC2/T11.11.27. RE AUTO SWITCH QUANTITIES These should be - (1) Shunt coil - similar and similarly placed to the cutout shunt coil at present standard. (2) Series coil - similarly placed to the series coil in the present standard cutout, but consisting of two layers of about 16 turns (or nearest) of 14 SWG. D.C.C. (3) Resistance coil - wound over series coil, to consist of about 18 1/2 ft. of 22 SWG. D.C.C. Eureka (We have plenty). There will probably be a little space over. Each of these coils is separately insulated and each connected to its own pair of terminals as shown on the rough diagram given you. The contacts of the auto switch, of which one is in connection with the core, should be connected to the two terminals so as to be parallel with the resistance. This gives you all the necessary particulars and I should be pleased if you would go ahead and as quickly as possible instruct three auto switches to this specification. We are anxious to get them running on the cars as soon as possible. EFC. | ||