The TCO (Thermal Cut-Off) responds to temperature by interrupting an electrical circuit when the operating and/or environ- mental temperature exceeds the thermal rating of the device. NTEs radial lead TCOs accomplish this when the internal fusible alloy is melted by reaching the temperature of the melting point of the alloy, forming two separate balls at the edges of the leads by surface tension of the alloy to permanently open the circuit. Axial-lead TCO devices presently predominate over radial-lead devices. This results, at least in part, from design difficulties that exist in manufacturing a reliable, inexpensive radial-lead TCO device. However, in many circuit applications radial-lead devices are preferable since they take up a smaller area on a printed circuit board. Their compact size enables ease of assembly into the smallest of transformers ensuring total thermal protection.