This little battery operated tone modulator was designed to plug into the front
of one of the many Millen grid dip meters. By inserting into the phone output jack
it will modulate the dippers oscillator so you can trace the signal in a nearby
The 90751 pictured here belongs to Greg Schwabauer, KB7WWD. He obtained it at a swapfest along with two 90651 Grid Dip Meters.