As part of the 200-year anniversary of the opening of the Stockton & Darlington on 27 September 1825, in Issue 213 (Mar-Apr 2025) we looked at the early developments of railway telecoms in the 1800s. This article now looks at developments in railway telecoms since 1900.
Post-1900, signalling control areas became larger and railway telecoms became even more important. It is possible for trains to move without signalling, but communications are essential to move and manage train services. Railway telecoms cover voice, data, and radio for rail operations, business, and passenger use. It can also cover commercial telecoms services.
Operational telecoms systems provide a number of key services. These include normal day-to-day voice and data communications, such as providing links to support the operation of signalling and electrification systems and to facilitate quick communications in the event of a problem or hazard including communications for those attending an incident. Operational verbal communications include the use by signallers to give instructions to drivers of trains, and to persons wishing to use level crossings. They are also used to take and give back line possessions, grant electric traction isolations for emergencies, and to facilitate engineering works.
Consider the following quotation: “One of the most interesting developments of modern times in connection with the working of our railway systems is the use that has been made of telecoms. It has introduced a new set of circumstances into the methods of train working and provided a much greater power of control.”
This could have been published in 2026, but in fact it appeared nearly 100 years ago in ‘Control on the Railways’ by Philip Burtt. So, the importance of telecoms in railway operations is not new.
The mid 1800s saw the introduction of telegraph communications alongside the development of railways. In 1876, the telephone was invented by Alexander Graham Bell and this revolutionised communications by allowing voice transmission over long distances. Railways were quick to adopt the new voice technology alongside the use of the telegraph. This allowed even greater centralisation of train control into the 1900s.
A signaller controls the safe movement of individual trains using safety critical signalling equipment, but it is controllers who manage the service and supporting infrastructure at a higher level, such as ensuring trains run to the timetable, staff are available to operate trains, rolling stock is in the right place, and that faults are attended to. The controller also manages incidents and perpetuations, and all this needs efficient reliable communications.
It was the Midland Company which pioneered railway control when it introduced a system for mineral train working at Masborough, near Rotherham, in 1907. A control was established at Newport sidings, with a control board and communication lines to regulate and control the flow of mineral traffic in the ironworks area of Middlesbrough, for a total length of about 50 miles.
Other railway companies quickly followed and, for example, the Lancashire & Yorkshire based its system of control at Victoria station, Manchester. When completed around 1917, this consisted of a large circular office with seventeen control boards, each representing one section of the Lancashire & Yorkshire system. On the upper part of the wall, the diagrams of the seventeen boards were combined into one diagram of the whole system. There was a controller in charge of each of the 17 sectional boards, and who was in telephone communication with the signallers in their area.
Soon the central control arrangements included passenger trains and rolling stock allocation as an integral part of the central control systems. As the technology evolved and improved, control locations, their size, and detailed operational practices evolved, particularly as railway organisations changed. Today, having a centralised control with telecoms connections managed by the railway infrastructure manager is as important than ever.
Telecoms links for the controls were initially provided using overhead pole routes with large diameter copper wires. Railways also sometimes facilitated pole routes for the Post Office (now BT). For example, The Midland Railway provided the trunk line from London to Carlisle using 800lb copper wires.
The control points consisted of keyboards and various methods of establishing calls to individual or multiple locations for group call conversations were developed. These included omnibus code-ringing battery-powered telephones, together with ‘box to box’ communication between signallers, often using only a single pair of wires. Eventually, the links were moved to multipair cables either suspended from the pole rotes, buried in the ground, or located in troughing routes. As areas grew bigger, multi-channel transmission systems were used to cover the distances involved. Keyboards evolved to use technology developed typically for the other industries and, eventually, touch screen ‘dealer boards’ became the dominant technology for railway control rooms.
Signal Post Telephones
Rule 55 required that if a train was held by a signal at danger, the signaller must be informed within three minutes, or immediately in fog or falling snow. This was achieved by the driver sending the fireman to the signal box. This was not a problem where the area controlled by each signal box was small, but as control areas became larger and signals were located further away from their controlling signal box it became necessary to provide a telephone at signals which became known as the Signal Post Telephone (SPT).
The basic principle of Rule 55 is still present in today’s Rule Book. The safety requirements for an SPT are that the signaller must only be able to talk to one driver at once. The signaller must always be aware of the identity or location of the calling party, and there must be no overhearing. This is to prevent one driver obtaining instructions intended for another.
A point-to-point direct line was the simplest implementation of an SPT. This could be achieved with a local battery-powered telephone at each end of the line to meet the safety requirements. This arrangement was only suitable for very small signal boxes with a few signals and the local battery telephones also needed frequent battery changes – especially if the SPT was left ‘off-hook’.
At larger signal boxes, small switchboards were provided to answer calls. This became known as the concentrator, as they ‘concentrated’ calls from many SPTs onto one telephone for the signaller. The concentrator provided a central secure battery supply for the telephone and there have been many different designs of concentrator over the years.
Concentrators evolved from key and lamp technology through to processor and software-controlled touch screen systems. However, the functionality of only one train driver being able to talk securely to one signaller, with no conference facility to prevent overhearing and miscommunication, has always required ‘railway only’ software. This continues to this day with the IP systems now in use. With a very small market for SPT systems this creates additional costs.
Electronic switching
In some cases, in terms of overall telecoms technology, railways have led the way. The use of teleprinters was a useful means of sending messages, and several regions within British Rail adopted circuit switched systems which required the sender to dial up the receiving station. A major innovation by the LM Region was an electronic message switched teleprinter network based at Crewe and known as Signal Transmit Receive and Distribute (STRAD), covering the whole of the LM Region. This permitted messages to multiple addresses to be sent to a central switch and stored until the receiving teleprinters became free.
Business telecoms initially consisted of manual switchboards and an interconnection to the public telephone network. Automatic electro-mechanical telephone exchanges replaced the manual switchboards, although along the North Wales Coast the manual switchboards were used until electronic exchanges were provided in the 1980s. Trunk lines were either directly on the open wires or by derived carrier circuits (1+1 or 1+4) using valve technology transmission equipment, some of which was procured from the military. These systems evolved using balanced copper pairs, then co-ax, and finally fibre to carry several, and nowadays many thousands, of individual channels.
By the mid-1960s, the National Telecommunications Plan (NTP) was introduced with Extension Truck Dialling (ETD) allowing dialled connections throughout the railway network. The electromechanical Strowger step-by-step exchanges were replaced by electronic exchanges in the 1980s. Since then, the electronic exchanges have been upgraded and replaced a number of times, and now Internet Protocol (IP) is the dominant technology. With most devices now being IP packet switch based, it makes interfacing far easier than traditional circuit switched networks.
In 1970, British Rail bought Total Operations Processing System (TOPS) from the Southern Pacific in the USA. This was initially aimed at tracking freight wagon locations, but the system soon expanded into other uses including train reporting. It required high quality data lines to be provided across the country. With the large increase in bandwidth from the 4MHz 960 channel transmission systems being provided by the NTP, analogue circuits were transposed into digital transmission by means of modems.
Today we hear a lot about the ‘digital railway,’ but the move to digital telecoms transmission by the use of multi-channel Pulse Code Modulation (PCM) was introduced between Euston and Bletchley in 1968, then the longest PCM system in the country. Digital telecoms multiplexing was used in Plesiochronous Digital Hierarchy (PDH) and Synchronous Digital Hierarchy (SDH) technology which became the standard technology in the 1980s.
After PDH and SDH transmission, IP packet switching transmission was introduced. This has dramatically increased the data carrying capacity and where a hundred years ago the data rate on the copper pole routes was the equivalent of a few bits, today’s fibre optic cables can carry terabytes of data if required. A byte being eight bits and typically one character, e.g., ‘a’, is one byte, with a terabyte being 1,099,511,627,776 bytes.
A problem with long distance copper circuits was induced voltages from electrification and power cables, and the need to immunise them against dangerous high voltages. This included using, for example, booster transformers, return conductors, and isolation transformers.
However, fibre optic cables are also immune from electromagnetic interference, and the ribbon fibre optic cables now being installed on the railway can consist of hundreds of individual fibres. Consider that just a few years ago a fibre optic cable could consist of 24 individual fibres, with an overall cable diameter similar to today’s 432 fibre cables.
Radio
Some railways had been using radio in the 1920s, but the use of radio for many was generally limited to a few local systems around major stations and freight yards. In the 1970s a nationwide system for general radio communications was developed and known as the National Radio Plan (NRP), then National Radio Network (NRN). This was initially equipped with operator-controlled switchboards to connect radios and telephones, followed by automatic calling from a key pad, and eventually with an inter-dialling interface to the voice telephone network.
While crude compared to modern mobile radio, the NRN was in advance of public mobile radio. Eventually, the NRN was adapted to form a facility for train drivers to contact a control room in an emergency, becoming the Overlay Radio Network (ORN), also known as the driver to shore system.
A secure radio system for driver to signaller communication was introduced in areas where Driver Only Operation (DOO) was provided and known as Cab Secure Radio (CSR). It had the same functionality as SPT systems, but without drivers having to leave their cabs. A form of in-cab signalling was also delivered 40 years ago by the Radio Electronic Token Block (RETB) system, further explained in Rail Engineer issue 216 .
Both NRN and CSR were replaced by Global System for Mobile Communications – Railway (GSM-R). This has been a huge success and the system is well-liked by train operators. It has been used to avoid life threatening situations on a number of occasions. GSM-R however uses 2G mobile technology which is fast becoming obsolete. Most mobile operators have shut down their 3G networks and todays systems are 5G. The GSM-R replacement will be Future Radio Mobile Communication System (FRMCS). This will be a huge project to ‘swap over’ from GSM-R. FRMCS is also likely to use higher frequencies and will need additional base stations. This will add an additional ‘green’ challenge, not to mention the cost involved.
It is costing millions to renew and maintain the SPT systems, which are hardly ever used now GSM-R is in place. It is never easy to remove a safety-related system, but the removal or dramatic reduction of SPTs is something Great British Railways must consider in order to save costs.
Data and CIS
In the 1980s, British Rail began modernising its telephone voice network with digital exchanges and replaced the, by then, ageing STRAD system with a new digital National Teleprinter Network (NTN). Data links also became vital to link Local Area Networks (LANs).
Customer Information Systems (CIS) were becoming increasingly sophisticated in the 1980s with digital displays replacing the flap indicators of the 1960s and sometimes linked to timetable and train describer systems to allow some automatic operation. Public Address (PA) systems were also provided by the telecoms function, and one development was the introduction of ‘long line’ systems. These provided the ability for remote announcements to many stations from a central control point over the telecoms network. Today, many PA systems provide high quality automatic recorded announcements, linked to CIS and timetable systems.
The clock system was another important telecoms asset before Global Navigation Satellite System (GNSS) clocks were introduced. Central master clocks controlled many slave clocks over the railway telecoms network, so that every clock showed the same time. Station CCTV, Wi-Fi, and cyber security are just three of the additional applications that railway telecoms engineers have had to learn and manage, and the technology changes so fast that there will many more applications to deal with.
The railway’s telecom networks are a core part of railway operations which cannot be outsourced with any degree of confidence or certainty. This has been attempted a number of times around the world, but often with the controlling railway company having to take back the outsourcing to ensure it keeps control of the technology. There will be commercial opportunities to generate income and share costs, but it’s important that this is achieved with the infrastructure manager retaining control.
The unnecessary costs of SPTs was mentioned by Andrew Haines at his final briefing to the railway press at which he regretted that Network Rail was unable to obtain dispensation to avoid providing SPTs on the new Leven Branch. Rail Engineer shares his view that safety authorities need to better consider the cost of risk mitigation measures that have minimal, if any, benefit.
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