This paper presents elementary circuit components which exhibit self-checking properties; however, which do not utilize any additional signals to indicate the fault. The fault is indicated by generating specific values at some of standard outputs of a given circuit. In particular, various evolved adders containing conventional as well as polymorphic gates are proposed with less than duplication overhead which are able to detect a reasonable number of stuck-at-faults by oscillations at the carry-out output when the control signal of polymorphic gates oscillates.