Inspection of butyl rubber underbridge insulators at Preston Brook and on M.S.J. & A. line on L.M. region during Nov 1973 (TM-ETR-019)

Butyl rubber underbridge insulators have been fitted on B.R. where clearances are tight for the passage of contact and catenary wires at 25 kV. The majority of the underbridge insulators are installed on the Lea Valley line on E.R. and on the M.S.J. and A line on L.M. Region, but...