THE SIGNAL BOX

BLOCK SYSTEM

BRITISH RAILWAY SIGNALLING INSTRUMENTS

Sykes & Co railway signalling instruments

Sykes Lock & Block instrument

Sykes Lock & Block instrument

Sykes & Co (who often marked their equipment "SYX") developed an early Lock & Block system that was so far ahead of other systems in terms of safety interlocking at that time that it became widely adopted by a number of railway companies. They were found on most of the constituent companies of the Southern Railway, on the Great Eastern, North British and elsewhere.

Illustrated here is an accepting instrument - depressing the central plunger would display in the lower portion of the bezelled glass area the words "TRAIN ON" with an impressive clunking noise. The full message was, in this case, "TRAIN ON FROM SELLING", the next box down the line.

Resting to the lower right is the "switch hook", which pivots over to mechanically prevent the plunger being pressed - this is placed in position when there is a train in section and also works the block indicator at the other end of the block section.

The upper segment would read "LOCKED (or FREE) TO STARTER", indicating whether the home signal would be free to be operated. The levers were interlocked with the instrument and both worked in connection with treadles operated by the passage of trains.

The brass discs slide to reveal keyholes for the dreaded "emergency key" which was the one feature of this system that let it down. The instruments could not cater for non-typical train operation, and abnormal moves required the instrument to be released by key.

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

Sykes Lock & Block instrument

At the opposite end of the block section, you would find instruments such as these. The right-hand instrument is the one that controls trains entering the section ahead, and has a block indicator above it in the form of a miniature signal arm.

The tablet below reads "DOWN STARTER LOCKED/FREE TO REEDHAM SWING BRIDGE" and is operated by the plunger at the next box.

The left-hand instrument is for an intermediate signal, having no plunger or indicator. It simply works in connection with treadles and the operation of the lever for the signal ahead and shows "4 LOCKED/FREE TO STARTER".

The Sykes system effectively monitored the location of trains, whether in the block section or between signals at the same box, always locking the signal behind the train until it has passed the next signal ahead.

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

Sykes Double-Arm Lock & Block instrument

Sykes Double-Arm Lock & Block instrument

A different kind of Sykes instrument was known, officially, as the "Sykes One-Wire Two-Position, Lock & Block instrument with Double-Arm Indicator.

On this type, the two miniature signal arms indicated the state of the block section on both lines to the adjacent box. The small knob to the right is the commutator, whilst the tapper key works the block bell - an unusual feature on the Southern Railway/Region as most bells were worked by plunger.

These instruments did not replace the normal Sykes instruments as illustrated above, but worked in conjunction with them.

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