Abstract We compare our correlations between theoretical circuit models and experimental results for OTS devices and DIACS while they undergo relaxation oscillations. OTS devices are of the type OFF-?-ON while DIACS show well defined OFF and negative resistance (NR) states. The excellent agreement between theory and experiments in DIACS gives additional support to the use of our circuital models in the interpretation of our OTS data. Experimental results for DIACS include dc and pulsed I–V characteristics, low level ac response, as well as relaxation and quasi-sinusoidal oscillations. We discuss the lack of experimentally observed quasi-sinusoidal oscillations in OTS in view of previous interpretation of chalcogenide threshold switches as time varying systems as opposed to OFF-NR-ON devices.