Signedmarked: 1 OHM FOR 15 AMPERES / Crompton & Co LTD CHELMSFORD No 106
FunctionShuts that are used with meters divert most of the electricity so that it does not pass through the meter. This extends the range of the meter without damaging it.
Historical AttributesWhite triangle (Paul Donaldson's mark) indicates it was used for teaching in the course Physics 3, Harvard University Physics Department in the 1920s.
ProvenanceFrom the Jefferson Physical Laboratory, Harvard University.