Abstract: A function generator for use in a synchro to digital (S to D) converter in which successive approximations of the digital output are made by switching between two chains of cascade connected operational amplifiers so that, as one chain is incremented to decrease the error signal appearing at the output of the chain, the other chain is coupled to control the error reduction operation until the aforementioned switching is completed, at which time the chains reverse roles.

Abstract: Method and apparatus for comparing and/or adjusting the frequency output of a frequency source, which method and apparatus is greatly simplified, and permits adjustment within a relatively short time interval and at a precision whose known difference is less than five parts in the 10.sup.12.The rubidium-controlled oscillator employed by the major networks to produce the 3.58 MHz subcarrier signal is utilized as a standard. Offsets made available at regular intervals by the National Bureau of Standards are utilized to indicate the frequency differences between the network standards and the United States Frequency Standard (USFS).