(under the class definition) Devices which include an envelope and which are defined by the degree of vacuum in the envelope.
(1) Note. The devices in the subclass contain no appreciable amount of gas and are intended to be operated as vacuum devices. However, merely defining a device as a vacuum device will not be sufficient to cause classification of the patent in this subclass unless the degree of vacuum is specified. Devices defined merely as vacuum devices are classified in the other appropriate subclass in this class.
SEE OR SEARCH THIS CLASS, SUBCLASS:
567, for devices with a gas or vapor in the envelope even though the device is not intended to be operated with ionization of the gas or vapor; if the claims state that the device contains a gas or vapor, the patent is classified in subclass 567 even though the pressure is such that the device has the characteristics of a vacuum device. see (1) Note, above.
577, for such gas or vapor devices where the pressure is only a hundred microns (0.1 mm.) or less.
