THE SIGNAL BOX

BLOCK SYSTEM

BRITISH RAILWAY SIGNALLING INSTRUMENTS

Spagnoletti railway signalling instruments

Spagnoletti Lock & Block instrument

Spagnoletti Lock & Block instrument

The preponderance of Sykes Lock and Block instruments could lead one to believe they were the only Lock & Block system in existence, but this isn't so.

The Metropolitan and the District Railways used a system based around the standard Spagnoletti Three-Wire Three-position instruments (as used on the Great Western) which incorporated interlocking between the keys that worked the block indicator and a treadle in the track that recorded the departure of a train from the block section.

These instruments would have been essential to the intensive service of the sub-surface suburban lines, but the metropolitan extended the system throughout its network, and the late surviving examples were at locations between Amersham and Aylesbury.

This particular example was at Wendover, more details of which can be found in the Photo Gallery.