细节
A demonstration Tessler coil,
unsigned, the tightly wound copper coil with vulcanite mounts, mounted on a mahogany plinth base -- 15in. (38cm.) wide; and a Post Office Box relay by F.E. Becker and Co., with glazed panels showing the copper wound coils, on plinth base -- 9.1/8in. (23.2cm.) wide
unsigned, the tightly wound copper coil with vulcanite mounts, mounted on a mahogany plinth base -- 15in. (38cm.) wide; and a Post Office Box relay by F.E. Becker and Co., with glazed panels showing the copper wound coils, on plinth base -- 9.1/8in. (23.2cm.) wide