Resistors Heritage

BI Technologies • IRC • Welwyn

TT Electronics plc is a global electronics company, distilled at the turn of the century from the engineering conglomerate TT Group plc, which had a history extending back to 1988. But the Resistors Business Unit carries a far longer heritage. BI Technologies, IRC and Welwyn are market leading brands within this group, all with track record in resistive component innovation of over seventy years. 

BI Technologies

Formerly Beckman Industrial, BI Technologies began in 1940 with a single innovation; the “Helipot” helical potentiometer (essentially a precision variable resistive divider) which is a principle still in use today. In the mid-1950s cermet (ceramic – metal) materials were developed to raise the operating temperature of resistive parts, and in the early 1960s, BI pioneered in the use of thick film materials to make compact resistor networks. The following decades saw a series of innovations in thin film precision networks, compact surface mount moulded networks, chip resistor arrays and power resistors.


Founded in 1923 in Philadelphia, PA, IRC has been an innovative leader in the design, development and manufacture of resistors throughout the entire life of the electronics industry. A catalogue from 1933 shows the early product range. A pioneer in resistive film technologies, IRC was the original developer of nichrome thin film resistors in the 1950s, achieving a step change in the level of precision available to designers. This was followed by the implementation of moisture resistant tantalum nitride films, invented by Bell Labs in the 1960s, and their development into a comprehensive portfolio of high reliability precision resistors and networks. Proprietary metal glaze technology was also developed as a means of delivering higher power density in high reliability applications. In the 1990s the growing demand for lower ohmic value resistors was met with proprietary thick film chips and by many innovations in the field of low ohmic value metal element parts. Today product development and manufacture continue at TT Electronics' thin-film centre of excellence at Dallas, TX. 


Welwyn Electrical Laboratories Ltd was established in 1937 in Welwyn Garden City, near London, UK. Many of the earliest products were vitreous enamelled wirewound resistors which developed over the years into the well-known green W20 series, together with cracked carbon film resistors. An early catalogue from the 1940s shows the products which were available when the company relocated to Bedlington, UK. Here the innovation continued with the development of an award winning tin oxide process, thick film and thin film processes, and in the 1990s, thick film on steel power resistors. But wirewound technology always remained important for Welwyn, and many process developments enabled higher ohmic values, higher surge energies and tailored fusing performance to be achieved.

Today TT Electronics continues to pursue innovations in the field of resistors. Our global development team is committed to an extensive programme of new product introductions, and our FAEs are available to identify and support custom product development. So if you do not find the product you need, we have always specialised in creating the resistors that designers need.