The latter were made by Westinghouse and were the first street lighting luminaires specifically designed for the then-new bright, energy-efficient, long-lasting mercury vapor lamps. Westinghouse introduced these fixtures in 1947 and were known as their OV-20.

Within this installation a pintype insulator was mounted atop the street light pole. The line wire utilized a strain or guy-wire insulator to provide an electrical "break" in the overhead line wire so that a connection from each side would enter the pole-mounted mercury vapor transformer (ballast) as shown. In other instances a porcelain transposition insulator was deadended on each side instead for the same purpose.