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A portable harmonic analyser built by the TelephoneManufacturing Co. Ltd was used last year by British Railways during a series of system tests carried out on the Colchester-Clacton line. So, 59 years ago, started a story in Electronics Weekly’s edition of January 18th 1961. The story continues: These formed part of the overall System Test …

This story continues at Harmonic Analyser Checks Railway Traction Interference

Or just read more coverage at Electronics Weekly