Single-needle block instrument
Cooke's single needle instrument 1845 for signalling on the Norfolk Railway.
The electric telegraph was first applied to the working of railway traffic by Sir W F Cooke in 1837. In 1842 he devised a scheme in which the line was to be divided into sections, each governed by its own telegraph, and into which no second train should be allowed to enter until the first one had been signalled clear of it.
This arrangement, now known as the "block system" was first tried on the Norfolk Railway, a single line between Brandon, Norwich and Yarmouth, in 1844-1845. Although it considerably reduced the chance of a collision, its use was not made compulsory until 1889.
This instrument was employed at Trowse Station, which was the Norwich terminus when the line was opened in July 1845. It has a single needle and a drop handle, the dial having the code alphabet marked upon its face.