Uses signal from discriminator of 6,000-Mc microwave receiver to stabilize frequency of local-oscil-lator klystron. Balanced silicon-diode input chopper lattice is excited at 3.5 kc, but only error signal from discriminator will unbalance network and pass 3.5 kc on to error amplifier.-M. C. Harp, Nonvacuum Devices Control Klystrons, Electronics, 32;7, p 68-70.