The operating margins of the Y-bar switch are analyzed for both the double-level-masking (DLM) and single-level-masking (SLM) implementations. It is found that while both implementations show similar performance, two additional failure modes not seen in the DLM are found in the SLM version: 1. Bubble collapse at the base of the Y bar. 2. Bubble stripout along the conductor. Both of these failure modes are associated with magnetization reversal in the NiFe of the conductor. These failure mechanisms can be mitigated by good geometrical design and by application of an appropriate pulse sequence during operation. © 1977, IEEE. All rights reserved.