to the cut off frequency can be controlled by the damping resistor ro the capacitive coupling of r0 differs from the prior art as this element is generally direct coupled the purpose of c0 is to minimize the power dissipation in the filter by increasing the shunt impedance across l at low frequencies where the voltage magnitude is highest dissipation is proportional to the square of the voltage across r0 at frequencies close to cut off of the filter the reactance of c0 decreases to an extent that the resistor r0 effectively dampens the resonance peak of the filter preventing an unacceptable amplification in the vicinity of cut off the voltage magnitude in the vicinity of cut off is much less than that at lower frequencies and dissipation is minimized referring to fig5 the model of the induction logging tool transmitter of fig4 in accordance with the present invention is shown again except that a filter f 12f connects the nodes between switches 12a 12b and 12c 12d to the inductor l 12e the transmitter coil across which another output signal vo is measured the filter f 12f converts the output signal v to the output signal vo across the inductor the output signals v and vo are illustrated in fig7 of the drawings fig5 a illustrates a more complete construction of the transmitter of fig5 in operation referring alternately to fig5 a and fig7 of the drawings during the time period between.