Signedunsigned except for larger knob marked: TYPE 200B VARIAC 115V 50-60Hz 1A / GENERAL RADIO CO. CAMBRIDGE, MASS. U.S.A.
FunctionThe Variac may have been used to adjust the gain of the incoming signal; the other controls allowed the experimenter to tune the phase of that signal so that it could be synchronized with signals emitted by different components in the NMR apparatus.
The experiments used two of these modulators, apparently identical; only one reached the Collection.
ProvenanceUsed in Harvard's advanced undergraduate physics lab (Physics 191r) before coming to the collection.