Electric train staff
Two machines are installed at either end of a single line section, and while each machine can hold several staffs, the machines are electrically interlocked so that only one staff can be released at a time. This staff must be carried by any train entering the section which the staff protects. The fact that only one staff can be withdrawn prevents multiple trains entering the same section thus ensuring train safety.
The staff instruments at either end of a section are connected by a pair of wires, which may also be used for a telegraph or telephone circuit. With no staff out, the two machines have the same polarity, which allows a staff to be extracted at one end or the other. Once extracted, the instruments have opposite polarity, which prevents another staff being extracted, hence the safety element of the system.
Each staff is labelled with the names of the stations at either end of the section, plus a number, which is recorded in the train registry book.
Staffs in a section have a particular arrangement of rings, a bit like the wards on a key, which prevents a staff being restored incorrectly to an adjacent section. There are typically three wardings so that sections can be amalgamated or divided as required, without having to alter the wardings of all sections in a cascade fashion.
When a train arrives to make a crossing, the staff should not be handed directly to the waiting train in the opposing direction, but rather, should be put through the machine, extracting a staff of a different number. This rule is necessary to give the opposing station a chance to decline to accept that train for any reason, such as
- shunting outside home signal
- prove direction stick relays down in any automatic level crossing
On the FR it is also necessary to do this in order to activate the automatic signalling systems.
Intermediate ETS and short sections
Where there are intermediate sidings, and it is desired to lock away a train, clear of the single line section, intermediate machines can be provided. Siding points mid section may be released by a key mounted on the end of some or all of the staffs, or a with Drawer-lock release.
Where an intermediate location on a long section has a loop it is possible to split the long section in two (or more) short sections. The long section token must be withdrawn from the intermediate instrument and used to unlock the short section working. The short sections have their own electric train staffs and instruments.
The first electric token system was invented by Edward Tyer and patented by him in 1878. It used round tablets with different patterns of notches to distinguish between those for different sections.
The electric train staff was invented on the LNWR in 1888 and licensed to the Railway Signal Co. of Liverpool. This system used the same working principle as the earlier tablet system, but the tokens were now in the familiar staff shape. The original electric train staffs were quite large and heavy, but a miniature version was introduced by the Railway Signal Co. in 1906.
A number of accidents on various railways illustrate the need for ETS, as well as its weaknesses:
- 1873 - Menheniot. This accident occurred before ETS or starting signals were installed. The signalman gave the verbal right-of-way to one driver called "Dick", not realising that the other driver was called "Dick" as well, causing a head on collision. 
- 1921 - Abermule. Porter and driver did not check that the names on the ETS were correct, causing a head-on collision. 
ETS on the FR
ETS replaced staff and ticket on the Ffestiniog Railway in 1912 and has been in use ever since. Some of the instruments and staffs currently in use date back to old company days. The FR uses Railway Signalling Co. instruments, predominately the miniature type except for the short sections Minffordd - Rhiw Goch and Rhiw Goch - Tan y Bwlch which use large staffs.
Usually there has to be an operator at each end of a section to release a train staff. On the revived FR this is often not the case as stations are usually unmanned. This problem was solved by Dan Wilson who invented and constructed the initial "remote operators" which make it possible for the fireman to release a train staff when the station at the other end of the section is unmanned. This rather unheralded piece of innovation has been a key part of FR train operations ever since.
The current ETS sections are as follows:
- Portmadoc - Minffordd - Note spelling of Portmadoc is as it appears engraved on staffs - Intermediate machine at Boston Lodge
- Minffordd - Tanybwlch - Long section - Intermediate machine at Rhiw Goch
- Can be split into two short sections either side of Rhiw Goch when full section token is placed in the frame at Rhiw Goch
Micro-ETS on the WHR
The original Welsh Highland Railway used the staff and ticket system. The modern railway currently also uses staff and ticket, however the FR Co. were anxious to obtain enough ETS instruments to equip the WHR. After a long search, sufficient ETS equipment to operate the entire railway was obtained in 2008 from the Irish national railway company Iarnród Éireann. The equipment became redundant after Iarnród Éireann recently modernised its signalling systems. Like that on the FR, the equipment obtained for the WHR is of the Railway Signal Co. miniature type.
As the WHR has no telephone cabling to connect the system, the FR Co. is developing a more modern alternative method of connecting the ETS machines. Until the system is finished, the WHR will continue using its current token systems. This new system obviates the need for telegraph lines by connecting the machines through the internet. This has led to the term "micro-ETS" being coined. By 2019, £225,000 had been donated by Ffestiniog Travel towards the costs of this project, with phase one of the project (Porthmadog to Rhyd Ddu) due to start the same year. Token machines will be installed at Porthmadog Harbour, Pont Croesor, Beddgelert and Rhyd Ddu. Intermediate machines at Pen y Mount and Hafod y Lynn are not planned at this time. 
The planned Micro-ETS sections are as follows:
- "Electric Token Block". Railway Signs and Signals of Great Britain. Retrieved 17 October 2018.
- Wikipedia Menheniot
- "Engineering the Welsh Highland Railway re-build". RailwayPeople.com. 15 August 2008. Retrieved 27 September 2008.
- "FR Company Information Release, 30.08.08". FR. 30 August 2008. Retrieved 30 August 2008.
- Marira Cook (2019) "Ffestiniog Travel", The Snowdon Ranger, Issue 105
- John Fenner (2019) "The 2019 Volunteer Liaison Meeting", Ffestiniog Railway Magazine, Issue 245, page(s): 360
- Tim Prent (2019) "Signals & Telegraph", The Snowdon Ranger, Issue 106, page(s): 12