Abstract: A carrying case for protecting heat sensitive materials includes a first portion, a second portion, and a closure device. The closure device seals the first portion to the second portion. Each portion includes a retainer which contains a phase change material. The retainer is covered on an outside with an insulation layer. The insulation layer and retainer are preferably covered with a fabric layer. A second embodiment of a carrying case for protecting heat sensitive materials includes a cover, a container, and a closure device. The walls of the container and cover preferably include a retainer which contains phase change material, an insulation layer, an outer fabric layer, and an inner fabric layer. A third embodiment of a carrying case for protecting heat sensitive materials includes a pouch which is sealable with a closure device. The wall of the pouch preferably includes a fabric outer layer, a flexible foam outer layer, a phase change layer, a flexible foam inner layer, and a fabric inner layer.

Abstract: An electronic gain control device including a first bipolar circuit having log transfer functional elements, preferably in the form of a pair of parallel first transistors of different polarities, and a second bipolar circuit including antilog transfer function elements, preferably a pair of second transistors connected in parallel and of opposite polarity. A gain control signal is summed with the log output signal of the first bipolar circuit to produce a second output signal antilogarithmically related to the first output signal and the gain control signal.The log and antilog transfer functional elements receive a bias signal of sufficient magnitude relative to the input signal that the entire circuit is in continuous electrical conduction in order to operate in a class A domain.

Abstract: A voltage controlled amplifier or multiplier circuit including a dual polarity rectifier for dividing the AC input signal into first and second unipolar signals, the first unipolar signal being the positive excursion of the AC input signal and the second unipolar signal being the inverted negative portion of the AC signal. Each unipolar signal is processed through a separate, conventional, unipolar log-antilog amplifier circuit, to each of which is applied a control voltage. The resultant unipolar signals are then subtracted in a differential amplifier to reconstitute the waveform of the original AC input signal, thereby producing the gain-controlled output signal.