Multistage, Cryogenically-cooled 4GHz Parametric Amplifier by the TRG Division of Control Data Corporation, c. 1967, fitted to the Goonhilly No. 2 satellite antenna for use with Intelsat II during the period 1969-73 approx. Multistage, Cryogenically-cooled 4GHz Parametric Amplifier by the TRG Division of Control Data Corporation 1967