A transfluxor analog memory using frequency modulation

The accurate storage of a continuous voltage has always proven to be a difficult and challenging problem to the designers of electronic analog systems. Most modern analog computer installations include a number of "sample-hold" devices, utilizing high-quality operational amplifiers in combination with special electronic switching circuitry. In such units the voltage is stored as charge on a capacitor, so that leakage and grid currents must be extremely carefully controlled to permit long-time storage with high accuracy. Recently introduced hybrid computer systems have placed an additional requirement upon the analog memory unit: economy. For example, in the discrete-space-discrete-time hybrid computer system now under development at UCLA, 1,000 sample-hold circuits will be required in order to accommodate 1,000 parallel digital-analog channels. Furthermore, hold times of several minutes are desired. Under these conditions conventional capacitor-type analog memories become economically unfeasible. These considerations have stimulated a search for a rapid, accurate and economic analog memory and have resulted in the development of the FM-transfluxor unit described in this paper. Since their introduction by Rajchman in 1955, multiaperture magnetic devices (MAD) have assumed an important place as magnetic logic and memory devices in digital computer applications. The extension of this technique to analog systems has been proposed from time to time, but no fully satisfactory transfluxor analog memory has been described to date.