  We examine the conditions under which a signed graph contains an edge or a
vertex that is contained in a unique negative circle or a unique positive
circle. For an edge in a unique signed circle, the positive and negative case
require the same structure on the underlying graph, but the requirements on the
signature are different. We characterize the structure of the underlying graph
necessary to support such an edge in terms of bridges of a circle. We then use
the results from the edge version of the problem to help solve the vertex
version.
