1. Since input and output of the amplifier are coupled directly, a zero drift δE at the input will produce a change δE of the output, without any signal having been received.
2. The gain of a practical amplifiercanbe made to approach infinity by the application of positive feedback. If we choose a sub-loop of gain m0 for this purpose, then we must make the feedback factor 1∕m0. Suppose now that m0 drifts in the course of operation to a new valuem. The resultant effective gain of the sub-loop will be mʹ = m∕(1−m∕m0), which changes sign according to whether mm0, ∣mʹ∣≥m0.
3. At the suggestion of Professor R. R. Wilson.
4. Type LA glass mike, Condenser Products Corporation, Chicago. Plastic dielectric condensers must be used to minimize the effects of dielectric hysteresis or “soakage.” In addition, they have excellent time constants.
5. In order to prevent “rectification” of spurious ac signals by the action of this discharge, it is necessary to shield the input to the integrator scrupulously. Without this precaution, or if ac pickup is present due to other causes, the integrator reset will become erratic, leaving positive or negative charges trapped on C1 at random.