Tyers Electric Train Tablet
Encyclopedia
Tyer's Electric Train Tablet system is a form of railway signalling
for single line
railways used in several countries; it was first devised in Great Britain by engineer Edward Tyer after the Thorpe rail accident
of 1874, which left 21 people dead. It was used in New Zealand for close to 100 years until June 1994.
The system used a hard disk called a tablet, a form of token
.
The purpose of the system was to use the tablet as a physical guarantee to the traincrew that their train had exclusive right of way on the single line section. Without this they could not proceed beyond the section signal which protected entry to the single line.
With advances in electrical locking of the lever frame
within the signal box
, the tablet instrument also electrically locked the section signal lever. This was marked with a white stripe on the red background.
There were various incarnations of instruments developed by Tyer & Co. Below are the more commonly found ones:
The Tyer's no. 7 tablet instrument consists of a wooden case, on top of which is a metal slide, a switch plunger, a bell plunger and an electric current indicator. On the front is an indicator which may show either of three indications: "Line Closed"; "Train Approaching" and "Train on Line". Below this there is a second slide, which has three positions: fully home, withdrawn half way, and fully withdrawn. The three indications correspond to the three positions of the slide. The case contains several tablets; they are removed from the instrument using the bottom slide, and replaced using the top slide. The instrument was so constructed that if a tablet had been withdrawn from either instrument of a pair, no further tablets could be withdrawn until the withdrawn tablet had been placed either in the other instrument, or in the same instrument from which it had been withdrawn.
The Tyer's no. 6 tablet instrument is cast iron framed that has a movable drawer at the front which issues and receives the tablets. On the left hand side is a lever to reseat the tablet when it is replaced into the magazine. It has wooden side cheeks to access the complicated mechanism and a tombstone shaped wooden case on the top which houses the bell plunger, commutator and the tablet indicators for up and down trains. At the very top was the galvanometer
. The signalling bell
associated with the machine is separate so could be located on the block shelf or wall mounted above the instrument.
To release a tablet at station A to send a train to station B:
To close up each machine once the train has arrived at station B from station A:
The Tyer's No. 6 instrument was originally a non-restoring design which meant once the tablet had been removed, it had to travel through the single line section and be replaced in its companion instrument to release the section again. This meant that should a train failure occur in the single line section or a shunt beyond station limits, the tablet had to travel to the receiving instrument by foot or horse.
However, there was a way in which a shunt could be performed without removing the tablet. This was achieved by a very similar means of the staff and ticket working system.
Later on as shunting became more complex and the trains longer requiring frequent movements on to the single line section to complete the shunt, many instruments were converted to restoring types, which enabled the tablet to be placed back into the issuing instrument for shunting out of station limits. This increased flexibility and did not compromise safety. It also dispensed with the written authority in the staff and ticket system.
used the Tyer's No. 7 electric train tablet instrument at several locations, including the Bampton
to section.
The Tyer's No. 6 tablet instrument was far more widespread in the UK and was adopted by most railway companies on single line installations. However, when the Tyer's No. 9 key token instrument was patented 40 years later in 1912, it began to replace the No. 6 due to it being compact, easier to use and had far less moving parts to service and repair.
On Britain's national network the use of Tyer's system is now almost extinct, with most lengthy single track lines having been converted to more modern systems such as Tokenless Block or Radio Electronic Token Block
. However, as of 2011 the Tyer Electric Token Block remains in use on the Stranraer Line
south of Girvan
.
The last tablet used on the New Zealand Rail Network was to allow train 1602 (Wellington - Masterton morning Wairarapa Connection) to travel between Featherston
and Masterton
on the Wairarapa Line
on Monday 4 July 1994. Even though the Masterton to Woodville tablet sections survived a few days longer, trains ran on a safe all where Train Control could allow a train to run without a tablet.
The last sections to use the tablet system were:
The instrument from which these photographs have been taken is still in full working order but retired from the railway.
Railway signalling
Railway signalling is a system used to control railway traffic safely, essentially to prevent trains from colliding. Being guided by fixed rails, trains are uniquely susceptible to collision; furthermore, trains cannot stop quickly, and frequently operate at speeds that do not enable them to stop...
for single line
Single track (rail)
A single track railway is where trains in both directions share the same track. Single track is normally used on lesser used rail lines, often branch lines, where the traffic density is not high enough to justify the cost of building double tracks....
railways used in several countries; it was first devised in Great Britain by engineer Edward Tyer after the Thorpe rail accident
Thorpe rail accident
The Thorpe rail accident occurred on 10 September 1874, when two trains were in head-on collision at Thorpe St Andrew in the English county of Norfolk....
of 1874, which left 21 people dead. It was used in New Zealand for close to 100 years until June 1994.
The system used a hard disk called a tablet, a form of token
Token (railway signalling)
In railway signalling, a token is a physical object which a locomotive driver is required to have or see before entering onto a particular section of single track. The token is clearly endorsed with the name of the section it belongs to...
.
The purpose of the system was to use the tablet as a physical guarantee to the traincrew that their train had exclusive right of way on the single line section. Without this they could not proceed beyond the section signal which protected entry to the single line.
With advances in electrical locking of the lever frame
Lever frame
Mechanical railway signalling installations rely on lever frames for their operation to interlock the signals and points to allow the safe operation of trains in the area the signals control...
within the signal box
Signal box
On a rail transport system, signalling control is the process by which control is exercised over train movements by way of railway signals and block systems to ensure that trains operate safely, over the correct route and to the proper timetable...
, the tablet instrument also electrically locked the section signal lever. This was marked with a white stripe on the red background.
Construction
An instrument was placed at each end of the single-track section that they were to control. They were connected together electrically in such a way that operation of one would depend on operations carried out using the other.There were various incarnations of instruments developed by Tyer & Co. Below are the more commonly found ones:
The Tyer's no. 7 tablet instrument consists of a wooden case, on top of which is a metal slide, a switch plunger, a bell plunger and an electric current indicator. On the front is an indicator which may show either of three indications: "Line Closed"; "Train Approaching" and "Train on Line". Below this there is a second slide, which has three positions: fully home, withdrawn half way, and fully withdrawn. The three indications correspond to the three positions of the slide. The case contains several tablets; they are removed from the instrument using the bottom slide, and replaced using the top slide. The instrument was so constructed that if a tablet had been withdrawn from either instrument of a pair, no further tablets could be withdrawn until the withdrawn tablet had been placed either in the other instrument, or in the same instrument from which it had been withdrawn.
The Tyer's no. 6 tablet instrument is cast iron framed that has a movable drawer at the front which issues and receives the tablets. On the left hand side is a lever to reseat the tablet when it is replaced into the magazine. It has wooden side cheeks to access the complicated mechanism and a tombstone shaped wooden case on the top which houses the bell plunger, commutator and the tablet indicators for up and down trains. At the very top was the galvanometer
Galvanometer
A galvanometer is a type of ammeter: an instrument for detecting and measuring electric current. It is an analog electromechanical transducer that produces a rotary deflection of some type of pointer in response to electric current flowing through its coil in a magnetic field. .Galvanometers were...
. The signalling bell
British absolute block signalling
The principle of the British absolute block system of railway signalling is to ensure the safe operation of a railway by allowing only one train to occupy a defined section of track at a time...
associated with the machine is separate so could be located on the block shelf or wall mounted above the instrument.
Tablets
Tablets are in the form of a disc made of metal or fibre (with a gunmetal weight at the top of the magazine) about 4.5 inches (114.3 mm) in diameter, engraved with the names of the stations between which it is valid, and also provided with notches (also called configurations) or other indentations to ensure that it would fit only one pair of instruments. They were often painted in distinctive colours as an additional visual identification in areas where consecutive sections could each be controlled using the same type of instrument.Operation
The system required each station at the end of each section to be staffed, the staff member would communicate with the staff member at the other end of the section with a bell code to release a tablet.To release a tablet at station A to send a train to station B:
- Both machines must be in a closed state
- Operator at station A sends a bell code to station B asking if line is clear for the train.
- If clear operator at Station B will repeat the bell code to acknowledge.
- Station A operator holds down the bell plunger
- Station B operator presses his/her switch plunger with one hand, and with the other pulls out the bottom slide half-way; the instrument now shows a "Train Approaching" indication
- Station B operator holds down the bell plunger
- Station A operator presses his/her switch plunger with one hand, and with the other pulls the bottom slide to its full extent; the instrument now shows a "Train on Line" indication and also releases a tablet from the lower slide
- Station A operator hand the tablet to the driver of the train heading to Station B
To close up each machine once the train has arrived at station B from station A:
- The train driver hands the tablet to Station B operator
- Station B operator draws out the top slide, places the tablet in it, and closes the top and then the bottom slide; the instrument now shows a "Line Closed" indication
- Station B operator sends a bell code to station A (denoting "Train out of Section"), holding the plunger down on the last stroke
- Station A operator holds down his switch plunger, and closes the bottom slide; the instrument now shows a "Line Closed" indication
- Both machines are now in closed states ready for the process to start again for another train
The Tyer's No. 6 instrument was originally a non-restoring design which meant once the tablet had been removed, it had to travel through the single line section and be replaced in its companion instrument to release the section again. This meant that should a train failure occur in the single line section or a shunt beyond station limits, the tablet had to travel to the receiving instrument by foot or horse.
However, there was a way in which a shunt could be performed without removing the tablet. This was achieved by a very similar means of the staff and ticket working system.
Later on as shunting became more complex and the trains longer requiring frequent movements on to the single line section to complete the shunt, many instruments were converted to restoring types, which enabled the tablet to be placed back into the issuing instrument for shunting out of station limits. This increased flexibility and did not compromise safety. It also dispensed with the written authority in the staff and ticket system.
Areas of use
The Great Western RailwayGreat Western Railway
The Great Western Railway was a British railway company that linked London with the south-west and west of England and most of Wales. It was founded in 1833, received its enabling Act of Parliament in 1835 and ran its first trains in 1838...
used the Tyer's No. 7 electric train tablet instrument at several locations, including the Bampton
Brize Norton and Bampton railway station
Brize Norton and Bampton railway station was a railway station south of the village of Brize Norton on the East Gloucestershire Railway between and . The station had two stone-built platforms, a station building and a goods shed....
to section.
The Tyer's No. 6 tablet instrument was far more widespread in the UK and was adopted by most railway companies on single line installations. However, when the Tyer's No. 9 key token instrument was patented 40 years later in 1912, it began to replace the No. 6 due to it being compact, easier to use and had far less moving parts to service and repair.
On Britain's national network the use of Tyer's system is now almost extinct, with most lengthy single track lines having been converted to more modern systems such as Tokenless Block or Radio Electronic Token Block
Radio Electronic Token Block
Radio Electronic Token Block is a system of railway signalling used in the United Kingdom. It is a development of the physical token system for controlling traffic on single lines.- How it works :...
. However, as of 2011 the Tyer Electric Token Block remains in use on the Stranraer Line
Glasgow South Western Line
The Glasgow South Western Line is a mainline railway in Scotland that runs from Glasgow to Kilmarnock, and then either via Dumfries, or Stranraer via Ayr, with a branch to East Kilbride.- History :...
south of Girvan
Girvan railway station
Girvan railway station is a railway station serving the town of Girvan, South Ayrshire, Scotland. The station is managed by First ScotRail, who operate all passenger services from there. It is on the Ayr to Stranraer section of the Glasgow South Western Line and is situated 62 miles south of...
.
The last tablet
Featherston
Featherston is a name of English origin, at least as old as the 12th century. The link with "Featherstone" is probably not traceable, but people researching both spellings contribute to the collection of pages in the website called "The Featherstone Society".The name is applied to people and...
and Masterton
Masterton
Masterton is a large town and local government district in the Wellington Region of New Zealand. It is the largest town in the Wairarapa, a region separated from Wellington by the Rimutaka ranges...
on the Wairarapa Line
Wairarapa Line
The Wairarapa Line is a secondary railway line in the south-east of the North Island of New Zealand, connecting the capital city of Wellington with the Wairarapa region. The line ends at Woodville, where it joins the Palmerston North - Gisborne Line...
on Monday 4 July 1994. Even though the Masterton to Woodville tablet sections survived a few days longer, trains ran on a safe all where Train Control could allow a train to run without a tablet.
The last sections to use the tablet system were:
- Featherston Railway StationFeatherston Railway StationFeatherston railway station is a single-platform, urban railway station serving the town of Featherston in the Wairarapa district of New Zealand. The station lies on the Wairarapa Line, and is located between Harrison Street West and Harrison Street East...
- Carterton Railway StationCarterton Railway StationCarterton Railway Station, in the Wairarapa district of New Zealand, is a single platform railway station in the town of Carterton. It is located at the corner of Cnr Broadway, Davy and Wheatstone Streets, near the main shopping precinct on State Highway 2...
- Masterton Railway StationMasterton Railway StationMasterton railway station is a single-platform, urban railway station serving the town of Masterton in the Wairarapa district of New Zealand. The station lies on the Wairarapa Line, and is located at the end of Perry Street. It is one hour, thirty seven minutes journey time to Wellington. Trains... - Masterton Railway StationMasterton Railway StationMasterton railway station is a single-platform, urban railway station serving the town of Masterton in the Wairarapa district of New Zealand. The station lies on the Wairarapa Line, and is located at the end of Perry Street. It is one hour, thirty seven minutes journey time to Wellington. Trains...
- Pahiatua - Pahiatua - Woodville Railway Station, New Zealand
Heritage railways and museums
Today the tablet system lives on in many heritage railways and museums either as static / operational / interactive displays or as part of the heritage railway signalling systemHeritage railways
- Ferrymead RailwayFerrymead RailwayThe Ferrymead Railway is a New Zealand heritage railway built upon the formation of New Zealand's first public railway, the line from Ferrymead to Christchurch, which opened in 1863. On the opening of the line to Lyttelton on 9 December 1867, the Ferrymead Railway became the Ferrymead Branch and...
, Christchurch - Silver Stream RailwaySilver Stream RailwayThe Silver Stream Railway is a heritage railway at Silverstream in the Hutt Valley near Wellington, New Zealand. It regularly operates preserved New Zealand Railways Department locomotives along a restored section of the Hutt Valley Line before a deviation was built in 1954.- History :The...
, Wellington - Glenbrook Vintage RailwayGlenbrook Vintage RailwayThe Glenbrook Vintage Railway is a steam railway in Glenbrook, New Zealand. One of New Zealand's premiere rail heritage sites, it is not a museum as such, but rather a fully self-supporting, operating steam railway, built almost entirely by volunteer labour...
, Auckland
Railway museums
- Carterton Community & Railway Museum, Carterton Railway StationCarterton Railway StationCarterton Railway Station, in the Wairarapa district of New Zealand, is a single platform railway station in the town of Carterton. It is located at the corner of Cnr Broadway, Davy and Wheatstone Streets, near the main shopping precinct on State Highway 2...
- Fell Engine MuseumFell Engine MuseumThe Fell Engine Museum in Featherston, New Zealand, is a museum based around the only remaining Fell railway locomotive in the world.This locomotive, number H 199, climbed up the Rimutaka Incline using John Barraclough Fell's unique method of four grip wheels on a raised center rail.H 199 is one...
, Featherston
Other
- New Zealand Railway and Locomotive SocietyNew Zealand Railway and Locomotive SocietyThe New Zealand Railway and Locomotive Society Inc is a society of railway enthusiasts, based in Wellington.The Society publishes a magazine, the New Zealand Railway Observer and a newsletter Turntable. The Society publishes books on railway subjects. There are currently about 25 books available,...
Ava Archive - Pahiatua Railcar SocietyPahiatua Railcar SocietyThe Pahiatua Railcar Society is a society located in Pahiatua, New Zealand, dedicated to the restoration of railcars and other locomotives and rolling stock formerly operated by the New Zealand Railways Department...
, Pahiatua Railway Station - Helensville Railway Station Trust
- Papatoetoe Railway Station Trust
- Taumarunui Rail Action Group
- Ormonville Railway Station
Internal workings
Below are a few photographs of the internal workings. This particular instrument has had the electric line clear addition and restoring functions added at a later date. It also carries the original plates by the plunger and commutator which were often removed.The instrument from which these photographs have been taken is still in full working order but retired from the railway.