Great Northern Three-Wire Three-Position block
Unlike many of the impoverished pre-grouping railway companies,
the Great Northern never made ant attempt to economise in telegraph wire by
using the complexities of one-wire blocks. Instead, they created their own
style of three-wire system, many of which were built out of old telegraph
instruments.
On the left is a pegging instrument, a straight conversion from a telegraph instrument by providing a pistol-grip trigger device to hold the commutator to the left or right.
The right-hand instrument is the non-pegger for the opposite line - here the base section of the telegraph instrument has been omitted as unnecessary.
Between the two instruments is the bell - which was encased in a timber box for neatness.
The example illustrated is at Blotoft Siding, more details of which will be found in the Photo Galley.