Retb definitions

Retb

1) Radio electronic token block
Found on https://www.crosswordclues.com/clue/retb

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RETB

radio electronic token block
Found on http://www.encyclo.co.uk/local/20497

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RETB

Radio Electronic Token Block, a signalling system for single lines.
Found on http://www.scot-rail.co.uk/page/Glossary

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