Pentrix, a manufacturer of Spectrum Analyzer plug-ins for the Tek 530/540 Series was acquired by Tektronix about 1964. They first designed the L10 for NASA. Following the acquisition, they designed the 1L20 and 1L30, and later the 1L5. These successes were followed by many other designs in what eventually became Frequency Design Instruments (FDI). This photo shows Arnie Frisch and Larry Weiss, two of the founders at their new Tektronix location, along with Rich Nute.

More information is available on our Spectrum Analyzer page and Tektronix Gets Into The Spectrum Analyzer Business written by co-founder Morris Engelson.