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Introduction

Radio Electronic Token Block (RETB) is the signalling system in use on the West Highland Line, the Kyle Line and the Far North Line.

Elsewhere, RETB was introduced on the East Suffolk line in 1985, and the Cambrian lines in 1988.

Similar in principle to Electric Token Block, RETB uses 'electronic' tokens issued to the driver by radio from a single control centre.

Items to be covered on this page:

CDU
Radio Channels
Reflective Stop boards
Token Exchange Points
Hydro-pneumatic points
Points set indicators
Long-section tokens
TPWS indicators

The Routes

North Highlands

Ness Viaduct (Inverness) - Dingwall
Dingwall - Kyle of Lochalsh
Dingwall - Georgemas Junction
Georgemas Junction - Wick
Georgemas Junction - Thurso

The Dingwall to Kyle line was the first to use RETB, being 'launched' on 6 July 1984, and becoming fully opertational from 28 October 1984. The Far North Line to Wick and Thurso was converted in November 1985.

These routes were initially controlled from Dingwall, and it was intended that the Inverness resignalling scheme would included the Inverness - Dingwall section. However RETB was extended to Inverness with control moved to the new Inverness Signalling Centre in August 1988 (Inverness RETB).

West Highland Lines

Helensburgh Upper - Crianlarich
Crianlarich - Oban
Crianlarich - Fort William Junction
Fort William Junction - Mallaig

RETB was introduced on the WHL in three phases and is controlled by two work stations in Banavie Signal box, which also controls the Caledonian Canal swing bridge.

The 'South' work station controls Helensburgh Upper - Crianlarich - Oban
The 'North' work station controls Upper Tyndrum - Fort William Junction - Mallaig

RETB operation started firstly on the Mallaig section from 7 December 1987. Helensburgh Upper - Crianlarich - Oban was converted from 27 March 1988, and finally Crianlarich - Fort William Junction on 28 May 1988.

Sixteen signal boxes were closed under the resignalling scheme.

The Fort William area is controlled by conventional signalling from Fort William Junction signal box.

Fort Willliam Jn was renamed from Mallaig Junction to avoid any confusion when using RETB. Similarly, Tyndrum Upper was changed to Upper Tyndrum to distinguish it from Tyndrum Lower on the Oban line.

A list of Radio frequencies used on the West Highland Line can be found here.

Inverness RETB workstation	Banavie South workstation	Banavie North workstation

The Trains

Initially Eastfield's Class 37/4 fleet and 3 Class 20s were equiped for RETB operation. From January 1989 Class 156 units worked the daytime passenger services.

Portable RETB equipment allows steam trains to operate on the routes.

Each train has a Cab Display Unit (CDU) with a unique 4-digit number.

Since Autumn 2003, RETB lines have also been fitted with TPWS.

Cab Display Unit (CDU) in a Class 156 Photo by dysgraphyk	CDU in steam locomotive 45407

Types of Electronic Token

Section Token : Authorises movement from the stopboard (or section signal) at the entrance of the section to the stopboard (or signal) at the next Token Exchange Point. Tokens may have a suffix to remind the driver to arrive in a siding or 'wrong direction' platform. For attaching moves at Crianlarich and Georgemas, a 'Loop Occupied' suffix is used.

Long Section Token: Authorises movement from the stopboard (or section signal) at the entrance of the section to a stopboard (or signal) ahead, without the need to stop at Intermediate Token Exchange Points.

Shunt Token: Allows shunting movements to take place at at Token Exchange Point, within the Station Limits boards, and prevents other trains from approaching the TEP.

Engineering Token: Allows track engineers to take possession of a Section between the Station Limits boards of two adjacent Token Exchange points.