W20 Wirewound Resistors Welwyn / TT Electronics W20 Wirewound Resistors are CECC approved and offer high stability and reliability. Suitable for harsh environments, Welwyn / TT Electronics W20 Resistors have an impervious lead-free vitreous enamel coating. In addition, these resistors feature high-power dissipation for their size and overload characteristics ideal for protection circuits.