The Bliley BCS-1A Frequency Standard was developed for the purpose of making available to laboratories and industrial organizations a frequency source which has a stability approaching that of a primary standard and at the same time will maintain this stability when used in portable or semi-portable service. The standard is designed to maintain a stability over a twenty-four hour period of 2 parts in ten million. The long term stability is 2 parts per million over a thirty day per iod without resetting, and over line voltage fluctuations of plus or minus 10%. The entire instrument is constructed for rugged service conditions, such as changes in ambient temperature, air pressure, and humidity. It was constructed with long life features such as the use of high rated capacitors, resistors, transformers, and other components, and the use of red based 10,000 hour tubes in the oscillator and automatic gain control circuits.