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).
Wiring diagram for a semi-earthed system.
| Identifier | ExFiles\Box 51\2\ Scan151 | |
| Date | 21th November 1923 | |
| SEMI-EARTHED SYSTEM. GRACER NO. 5 S.P.T. Switchbox Head Lamps Side & Tail Head Dim Off Green 40/36 Red 40/36 Black 40/36 Red and Black 40/36 Brown & Red 40/36 Dynamo A B Red and Black 30 Cut Blue 30 Cut Black and White 40/36 Weston Ammeter 2-pole combined Fuse Starter motor Thru starter relay switch to frame Black & White 61/35 Rear roller blind Thru' Ignition switch Speedo Light Thru' M {Mr Moon / Mr Moore} /A switch Horn Push Thru' Head Leads to frame Stop Lt. Switch Light - N.C. Thru' Earth wire to chassis Battery | ||