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Section 19: Communications Signs

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By the early 1920s, telephones were being installed at the lineside for the use of traincrews, mostly at stop signals remote from the controlling signal box. Radio communication became an established feature on Britain's railways from the 1980s and spread rapidly until the whole network came to be covered by at least one form of radio system. The original analogue systems have been supplanted by newer digital systems.


By 1927, the Southern Railway was applying black and white diagonal stripes [19.1] to the cabinets housing signal post telephones, for identification purposes. The driver of a train detained at a signal provided with a signal post telephone was required to wait for a prescribed number of minutes before using it to communicate with the signalman. On the Southern Railway, the waiting time was originally set at one minute; this was later increased to three minutes, or five minutes in the London area. On other railways, a waiting time of two minutes was usually prescribed.

While the Southern Area of the LNER adopted the Southern Railway's method of marking signal post telephone cabinets with black and white diagonal stripes, the LNER's North Eastern Area opted to identify its telephone cabinets with a plate bearing the word "phone" in white on a black background [19.2].

[19.1] Signal Post Telephone Sign.
Area: Southern Railway (subsequently All Areas)   Usage: High   Status: Current
[19.2] "Phone" Sign.
Area: LNER   Usage: High   Status: Obsolescent

There was a requirement on electrified railways for telephones to be provided at the lineside at no more than 500 metre intervals. The Manchester - Sheffield - Wath line was electrified with the 1,500 V DC overhead wire system in two stages, completed in 1952 and 1954. Electrification telephones on this line were identified by a sign similar to the signal post telephone sign (see [19.1]), with the addition of a red band at the bottom [19.3]. The main section of the route closed in July 1981, and the remaining 1,500 V DC electrification at the Manchester end was converted to 25 kV AC in December 1984.

The standard sign for an electrification telephone depicts a telephone handset and the word "electrification", both in red on a white background [19.4]. Small signs showing a black telephone handset and arrow on a yellow background [19.5], which were usually affixed to overhead line structures, indicated the direction of the nearest electrification telephone.

[19.3] Electrification Telephone Sign.
Area: M-S-W line   Usage: Medium   Status: Historical
[19.4] Electrification Telephone Sign.
Area: All Areas   Usage: High   Status: Current
[19.5] Electrification Telephone Direction Sign (e.g. nearest telephone located to left).
Area: All Areas   Usage: High   Status: Uncertain

A new sign comprising a white square with a black St. Andrew's cross [19.6] was introduced in January 1962 to distinguish lineside telephones not located at signals (excluding electrification telephones) or telephones at signals where Rule 55 (see Section 9) does not apply (e.g. signals not on running lines or loops).

[19.6] Telephone Sign. Click Here for Photo
Area: All Areas   Usage: High   Status: Current

In September 1982, emergency lineside telephones were installed at intervals along the Absolute Block section between Crewe Steel Works and Beeston Castle & Tarporley signal boxes (London Midland Region). Signs showing a black telephone handset and arrow on a yellow background were attached to the mileposts (see Section 28) to indicate the direction of the nearest emergency telephone.

The provision of an in-cab radio system was a specific safety requirement to enable the introduction of "Driver Only Operation" (DOO), meaning the working of trains without a guard. The radio allows the driver to remain in the cab and communicate with the signalman when stopped at a signal, rather than using the signal post telephone. The original "DOO Radio" was introduced c.1981 on the lines between London King's Cross and Welwyn Garden City / Hertford North (Eastern Region), and between London St. Pancras and Bedford (London Midland Region). A development of the DOO Radio system was implemented in the Glasgow area in 1986, this being referred to originally as the "Strathclyde Manning Arrangement" (SMA). Subsequently, the same system was established in the Liverpool and London areas, and it became known as "Cab Secure Radio" (CSR). The system was secure, in that the driver and signalman could communicate on a one-to-one basis and not be heard by anyone else. The signalman had the facility to transmit a general message to all drivers in a particular area.


A different radio channel applied to each area under the control of a particular signalman. Channel changes were normally performed automatically, although lineside signs were provided at the boundary from one radio zone to the next and at places where the 'set up' procedure was usually carried out. The original channel indicator signs comprised a white diamond-shaped board with the appropriate channel code in the centre [19.7].

[19.7] Radio Channel Indicator.
Area: All Areas   Usage: High   Status: Historical

Radio systems were installed on some lines in the north of Scotland in the early 1980s in preparation for the eventual introduction of Radio Electronic Token Block (RETB) signalling, which uses the radio network for the transmission of electronic tokens and for verbal communication between train and signalman. Some rather basic signs were installed at the places where the channel had to be changed [19.8 & 19.9]. When the Regional Operations Manager travelled over the Aberdeen to Inverness line in November 1985, he saw what he referred to as "painted bits of wood with radio channel change information on them". He demanded that they be changed to circular or octagonal boards with yellow letters on a blue background, but this did not happen.

[19.8] Channel Change Board.
Area: Dingwall - Kyle of Lochalsh   Usage: Low   Status: Historical
[19.9] Channel Change Board. Click Here for Photo
Area: Aberdeen - Inverness   Usage: Low   Status: Historical

The National Radio Network (NRN) originated around 1979. Originally used only by engineering staff on the lineside, by the mid 1980s it was in widespread use in driving cabs. Train drivers could use the system to access the railway telephone network from inside the cab. NRN was not a 'secure' system like CSR. The provision of NRN ended the requirement for dedicated electrification telephones on AC overhead electrified lines, apart from inside tunnels, and led to many of them being removed. The NRN could be used by the driver to contact the signalman when detained at a signal without a signal post telephone or where the telephone was not located in a position of safety. At these signals, a sign was provided stating the telephone number for the signal box concerned (see [9.47 - 9.50]).


Drivers were required to manually set the NRN radio to the correct channel for the area that the train was in and to change channels as the train moved from one radio zone to another. As with CSR, signs were provided at places where the channel needed to be changed, and they showed the channel code that applied in the area ahead. A later design of radio channel indicator (in use by 1985) had the white diamond set against a black background with semicircular edges at the top and bottom [19.10]. This form of indicator was also used for displaying CSR channels and RETB channels. The first RETB installation was brought into use between Dingwall and Kyle of Lochalsh (Scottish Region) in October 1984.

[19.10] Radio Channel Indicator.
Area: All Areas   Usage: High   Status: Historical

Procedures were introduced on the Southern Region from c.1988 to prevent drivers from using the signal post telephone at certain signals while there was danger from trains passing on an adjacent line. Where this applied, the telephone cabinet was given a special sign bearing a yellow roundel superimposed on a black cross [19.11] instead of the usual black and white diagonally striped sign (see [19.1]). The driver of a train detained at a signal where this sign was exhibited was required to remain in the cab and await instructions. Once the signalman had stopped trains running on the adjacent line, the driver of the detained train would be advised by handsignalman, by a member of staff travelling on a train on another line or by radio that it was safe to leave the cab and go to the telephone.

[19.11] Signal Post Telephone Sign - Limited Clearance.
Area: Southern Region (subsequently All Areas)   Usage: High   Status: Obsolescent

For a period, two radio systems were in use over the lines controlled from Inverness (RETB) Signalling Centre. Locomotives were fitted with the original Band 2 radio equipment, while the Class 156 'Sprinter' DMUs, introduced from 1989, used Band 3 equipment. Two different channel codes thus applied over any given section of line. The signs showing the original Band 2 codes were altered to have a yellow background [19.12] to distinguish them from the new Band 3 signs, which had the usual white background. The Band 2 signs were removed c.1992.

[19.12] Band 2 Radio Channel Indicator (RETB).
Area: Far North Lines   Usage: Medium   Status: Historical

Where CSR was in use, drivers were required to go through a 'set up' procedure, which involved entering a four-digit radio identification number into the system. In most cases, the number shown on the signal identification plate (see Section 9) was used for this purpose, leading zeros being added as necessary to make up the four digits. At some locations, however, a distinct radio identification number had to be used (because two or more signals in the vicinity may share the same number, albeit with different prefix letters). Where such circumstances applied, the radio identification number was shown on a separate plate, termed an 'alias' plate. The alias plate, introduced in 1992, had white figures on a blue background [19.13]. An alias plate may also be provided at a location where no signal exists.

[19.13] CSR Alias Plate. Click Here for Photo
Area: All Areas   Usage: High   Status: Historical

A revised style of sign to identify signal post telephone cabinets located in areas of restricted clearance was introduced in 1995. The yellow roundel of the previous sign (see [19.11]) was retained, but the St. Andrew's cross was replaced by diagonal stripes [19.14] to be consistent with an ordinary signal post telephone sign (see [19.1]).

[19.14] Signal Post Telephone Sign - Limited Clearance.
Area: All Areas   Usage: High   Status: Current

In 1996, new radio channel indicators were introduced for each of the three radio systems then in use. The new signs, rectangular in shape, each bore the initials of the radio system to which they applied [19.15 - 19.17]. Additionally, the channel indicator for the secure CSR system [19.15] had a different background from the signs for the other two non-secure systems.

[19.15] Radio Channel Indicator for CSR. Click Here for Photo
Area: All Areas   Usage: High   Status: Historical
[19.16] Radio Channel Indicator for NRN.
Area: All Areas   Usage: High   Status: Historical
[19.17] Radio Channel Indicator for RETB.
Area: All Areas   Usage: Medium   Status: Historical

Although no sign was usually provided at the point where radio coverage ended, CSR termination boards [19.18] were installed on the Grain branch and at Bletchley, and an NRN termination board [19.19] was installed at Barking. The termination boards were similar in appearance to the ordinary radio channel indicators, with the addition of a red diagonal cross. Note that the NRN termination board at Barking had the wrong style of background.

[19.18] CSR Termination Board. Click Here for Photo
Area: Various   Usage: Low   Status: Historical
[19.19] NRN Termination Board. Click Here for Photo
Area: Barking   Usage: Low   Status: Historical