Physical description
Drawing in ink on paper, titled "Resistance Diagram for Dick Kerr Boxes", showing the set out of the resistance grids, the steps and the values in Ohms, of resistance for trams fitted with this type of equipment.
Drawing in ink on paper, titled "Resistance Diagram for Dick Kerr Boxes", showing the set out of the resistance grids, the steps and the values in Ohms, of resistance for trams fitted with this type of equipment.