THE SIGNAL BOX

BLOCK SYSTEM

BRITISH RAILWAY SIGNALLING INSTRUMENTS

Tyer & Co railway signalling instruments

Tyer's One-Wire Two-Position block instrument

Tyer's One-Wire Two-Position block instrument

Tyer & Co. produced a range of two-position instruments for different railways, and more or less cornered the market in early block signalling days. The instruments were unduly complex, owing to the desire to operate the block needles for both lines of a double track, and the bell, over one telegraph wire.

This also limited the functionality of the instrument, and it was only possible (without further complexity) to show two block indications. These were, basically, "Train on line" or "Train not on line" to indicate the state of the block section. This was achieved by miniature signal arms representing the starting signal at the box concerned, and the one on the opposite line at the next box. In simple terms, the starting signals at the boxes concerned should correspond to the indication given.

The two plungers operate the same block bell - the significant difference between them being that the top plunger raised, and the lower plunger lowered the accepting indicator.

This example was at Dorking, more details of which will be found in the Photo Gallery.

Great Eastern One-Wire Two-Position block instrument

A variation on a theme - this is the Great Eastern's version of the Tyer's One-Wire Two-Position instrument. Conventional indicators have supplanted the signal arm idea, and the two plungers have been placed horizontally. These are covered by swingable flaps to assist the signalman in identifying the state of the block section.

Immediately beneath the instrument is a standard Tyer's plunger unit, which allowed the bell to be rung to the next box without interfering with the signal indications.

To the left is a modern luxury - a Welwyn Control release.

This example was at Reedham Junction, more details of which will be found in the Photo Gallery.

Tyer's One-Wire Three-Position block instrument

Tyer's One-Wire Three-Position block instrument

Tyer & Co worked hard on developing a three-position instrument that would still work over one telegraph wire, and this was the result. They did not achieve huge popularity, owing to their use of varying voltage giving problems with longer block sections, but the Brighton, Furness and North Staffordshire Railways used them extensively.

Operation was through the rotation of the central commutator, which worked a mechanical indication visible above it. No effect was made on the block indicators at either end of the block section, however, until the plunger in the centre of the commutator was operated to ring the block bell.

This example was at Reedham Junction, more details of which will be found in the Photo Gallery.

Tyer's Three-Wire Three-Position Permissive block instrument

Tyer's Three-Wire Three-Position Permissive block instrument

Tyer & Co. also built more conventional three-wire instruments. This one is of a type found on goods lines of the Great Central Railway, although similar instruments with minor variations would be found on other companies' lines.

As with the instrument above, the bell plunger is located in the centre of the commutator wheel, although on this type of instrument the operation of the needle is not interlocked with the bell.

The number of trains in the permissive section are also indicated in the small window. The plunger on the right is used for each train to ensure only one train is recorded at a time.

This example was at Woodhouse East Junction.

Tyer & Co F pattern block instrument

Tyer's "F" pattern block instrument

This is a far more modern three-wire instrument form the Tyer factory, perhaps dating from the 1930's. The ornateness has been abandoned in the interest of a neat combined instrument.

The commutator is a neat and efficient rotating handle, whilst the bell is operated by the small plunger at bottom right. Return bells are heard through the gauze panel on the sides of the instrument, for the bell itself is hidden inside.

This type of instrument seems to have only been used by the Scottish Division of the LMS, although a few similar instruments existed in the London area on former Great Northern territory.

This example is at Larbert North.

Tyer's Black Box block instrument 

Tyer's Black Box block instrument

If there is an official name for this crude design of instrument, nobody seems to know it, for it is simply known as the "black box" instrument in official and unofficial circles.

The type was probably introduced in the late 1940's, in the post-war austerity. The use of brass and varnish has been abandoned, the wooden cases simply being painted black.

A neat and reliable instrument nevertheless, they were to be found anywhere on the LNER network.

These examples were at High Ferry, more details of which will be found in the Photo Gallery.

Tyer's No.6 Tablet Instrument 

Tyer's No.6 Tablet Instrument

Tyer & Co manufactured a range of single-line instruments, too, and one of the most widespread was the No.6 pattern.

This was one of many types of instrument designed to replace One Engine in Steam or Train Staff & Ticket working methods to allow more flexibility of working without allowing more than one train into the single line section.

An instrument such as this was provided at each end of the section, and each was loaded with single-line "tablets", only one of which could be withdrawn from either instrument at any one time.

The Tyer's tablet instruments were unduly complicated - requiring the bell plunger (centre) to be held in for three seconds which allows him to withdraw the slide (chocolate machine-style) to obtain the tablet. Many other manipulations and operations are involved - too many to go into here.

This example was at Cromer, more details of which will be found in the Photo Gallery.

Tyer's No.5 Permissive Tablet instrument

Tyer's No.5 Permissive Tablet instrument

This is a rare permissive instrument used for special purposes. The original function may well have been to allow more than one train on a single-line section (travelling in the same direction, of course) but the later use of this example was quite different.

It was used to signal trains over a single line which could be divided into two by opening an intermediate block post. Trains were kept apart by block working using Tyer's One-Wire Three-Position block between the three boxes, but the tablet instruments were only provided at the ends of the single line.

This example was at Reedham Junction, more details of which will be found in the Photo Gallery.

Tyer's Key-Token instrument

Tyer's Key-Token instrument

As time progressed, Tyer & Co somehow discovered that their massive and clumsy tablet instruments didn't need to be so, and along came the neat and tidy key-token instrument.

A key-tokens could be withdrawn when the signalman held in his bell plunger at the other end of the section (the knob on the right) provided a token wasn't already out, of course!

The electrical section indicator was not provided on all instruments - some had a manual indicator.

Most instruments were painted red - this one is an exception.

This example was at Thornton Yard, more details of which will be found in the Photo Gallery.