Abstract: A vapor heated roll used to heat material that spirally travels along the length of the roll has a vapor chamber that tapers from each end toward a specified location intermediate the ends to provide a chamber having an increasingly greater cross section from each end of the chamber to the specified location. A means for removal of condensate from the chamber is positioned at the location of largest diameter. The distance of the location for condensate removal from the point at which material enters upon the roll surface is calculated to provide maximum heating efficiency.

Abstract: In order to maintain a balanced load between power rectifiers operating in parallel within an uninterruptible power system, individual closed loops are established for regulating the direct current voltage at the output of the rectifiers and an open loop generates a reference voltage for each of such regulations. An operational amplifier is used as a current source to develop a current representative of the load in a particular rectifier. Parallel current dissipating resistors between each rectifier line and a floating potential common to all rectifier lines generates a reference voltage which is proportional to the average of such current dissipations and represents the average rectifier load.

Abstract: Disclosed is a test system primarily designed for free field testing of the hearing of an individual utilizing phase modulation to reduce or eliminate the production of standing waves thereby permitting accurate determination of pure tone hearing acuity. The test system consists of an audio signal source which may be the continuous or pulsed sine wave output of an audiometer, audio frequency signal generator, audio oscillator, or tape recorder wherein said stimulus signal is applied to a phase modulator. The phase modulator may be either an electronic or mechanical device or any combination thereof for periodically shifting the phase of the stimulus signal a predetermined amount. The phase modulated signal may be applied directly to an acoustic transducer or transducers if of sufficient amplitude or it may be amplified by an audio amplifier or amplifiers prior to such application.