Kelvin Hughes indicating controller Mk. IV (photo-transistor type) for thermocouple operation, use to control the temperature inside a lamp box, by Kelvin & Hughes (Industrial) Limited, London, 1945-1958
Kelvin Hughes indicating controller Mk. IV (photo-transistor type) for thermocouple operation, use to control the temperature inside a lamp box, by Kelvin & Hughes (Industrial) Limited, London, 1945-1958