GLOSSARY OF TERMS USED IN THE QUARTZ OSCILLATOR-PLATE INDUSTRY Actiaity: A rather loose term used to describe the relative magnitude of oscil

Actiaity: A rather loose term used to describe the relative magnitude of oscil lations, produced when an oscil lator-plate is excited in an electronic circuit. It is generally expressed in terms of the rectified grid current measured by a milliammeter inserted in series with the grid of the vacuum tube. It can also be expressed quantitatively as the coupling between the electrical and mechanical systems which is a simple function of the piezoelectric and elastic moduli of the vibration involved and the dielectric constant of the crystal plate. Ageing: The deterioration of some finished quartz oscillator-plates which initially drift upwards in frequency and downwards in activity with age. It is thought due to an unstable thin cracked and strained layer on the surface of the plate caused by abrasive action during finishing. This layer may be removed by etching to avoid deterioration of the plate. Air Gap: The distance between the surface of the electrode and the oscillator-plate. It is usually necessary to avoid particular gap dimensions in which resonance damping occurs with acoustic waves generated by the oscil lator-plate. AT Bar: A bar cut fromX sectionswith its long direction making an angle with Z equal to the complement of the AT angle (or 90"-35o15': 54'45',). Baloney Slicing: A name given to the process in which wafers in the approximate BT or other desired orientation are cut directly from the mother crystal, usually of prismatic habit. Bar: An elongated bar-like segment of rectangular cross-section cut in a particular direction across a section. The orientation and dimensions of the bar are usually so arranged that blanks are cut perpendicularly therefrom in approximately the correct position. Beat Frequency Oscillator.' A device whereby the output of a variable frequency oscillator is combined with that of a fixed frequency oscilIator in a rectifier or detector. The output will then contain among other constituents a current of a frequencyequal to the difierence in frequency of the two oscil lators, i.e., a beat frequency. Blanks: A term applied to qlartz plates with approximately or exactly the correct edge dimensions but not yet finished to final thickness (frequency). Ordinarily applied to pieces of quartz that are in the pfocess of being machine lapped or that are diced out but not yel lapped.