|  | G |
SECTION G — PHYSICS

|  | G |
Note(s) In this section, the following term is used with the meaning indicated: "variable" (as a noun) means a feature or property (e.g., a dimension, a physical condition such as temperature, a quality such as density or colour) which, in respect of a particular entity (e.g., an object, a quantity of a substance, a beam of light) and at a particular instant, is capable of being measured; the variable may change, so that its numerical expression may assume different values at different times, in different conditions or in individual cases, but may be constant in respect of a particular entity in certain conditions or for practical purposes (e.g., the length of a bar may be regarded as constant for many purposes). Attention is drawn to the definitions of terms or expressions used, appearing in the notes of several of the classes in this section, in particular those of "measuring" in class Fulltext... Hierarchy... Expanded...G01 and "control" and "regulation" in class Fulltext... Hierarchy... Expanded...G05. Classification in this section may present more difficulty than in other sections, because the distinction between different fields of use rests to a considerable extent on differences in the intention of the user rather than on any constructional differences or differences in the manner of use, and because the subjects dealt with are often in effect systems or combinations, which have features or parts in common, rather than "things", which are readily distinguishable as a whole. For example, information (e.g., a set of figures) may be displayed for the purpose of education or advertising (Fulltext... Hierarchy... Expanded...G09), for enabling the result of a measurement to be known (Fulltext... Hierarchy... Expanded...G01), for signalling the information to a distant point or for giving information which has been signalled from a distant point (Fulltext... Hierarchy... Expanded...G08). The words used to describe the purpose depend on features that may be irrelevant to the form of the apparatus concerned, for example, such features as the desired effect on the person who sees the display, or whether the display is controlled from a remote point. Again, a device which responds to some change in a condition, e.g., in the pressure of a fluid, may be used, without modification of the device itself, to give information about the pressure (Fulltext... Hierarchy... Expanded...G01L) or about some other condition linked to the pressure (another subclass of class Fulltext... Hierarchy... Expanded...G01, e.g., Fulltext... Hierarchy... Expanded...G01K for temperature), to make a record of the pressure or of its occurrence (Fulltext... Hierarchy... Expanded...G07C), to give an alarm (Fulltext... Hierarchy... Expanded...G08B), or to control another apparatus (Fulltext... Hierarchy... Expanded...G05). The classification scheme is intended to enable things of a similar nature (as indicated above) to be classified together. It is therefore particularly necessary for the real nature of any technical subject to be decided before it can be properly classified.

INSTRUMENTS

|  | G09 |
EDUCATING; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS

|  | G09C |
CIPHERING OR DECIPHERING APPARATUS FOR CRYPTOGRAPHIC OR OTHER PURPOSES INVOLVING THE NEED FOR SECRECY (secret communication Fulltext... Hierarchy... Expanded...H04K; arrangements for transmitting secret digital information Fulltext... Hierarchy... Expanded...H04L 9/00)

|  | G09C 1/00 |
Apparatus or methods whereby a given sequence of signs, e.g. an intelligible text, is transformed into an unintelligible sequence of signs by transposing the signs or groups of signs or by replacing them by others according to a predetermined system (cryptographic typewriters Fulltext... Hierarchy... Expanded...G09C 3/00)

|  | G09C 1/02 |
· | by using a ciphering code in chart form

|  | G09C 1/04 |
· | with sign carriers or indicators moved relative to one another to positions determined by a permutation code or key, so as to indicate the appropriate corresponding clear or ciphered text

|  | G09C 1/06 |
· | wherein elements corresponding to the signs making up the clear text are operatively connected with elements corresponding to the signs making up the ciphered text, the connections, during operation of the apparatus, being automatically and continuously permuted by a coding or key member

|  | G09C 1/08 |
· · | the connections being mechanical

|  | G09C 1/10 |
· · | the connections being electrical

|  | G09C 1/12 |
· · · | comprising contact-bearing permutation discs

|  | G09C 1/14 |
· · | involving removable or interchangeable coding numbers, e.g. master tapes, punched cards

|  | G09C 3/00 |
Typewriters for ciphering or deciphering cryptographic text (marking record carriers Fulltext... Hierarchy... Expanded...G06K)

|  | G09C 3/02 |
· | with auxiliary keys or keyboards acting on the original keys or keyboards

|  | G09C 3/04 |
· | wherein the operative connections between the keys and the type-bars are automatically and continuously permuted, during operation, by a coding or key member

|  | G09C 3/06 |
· · | the connections being mechanical

|  | G09C 3/08 |
· · | the connections being electrical

|  | G09C 3/10 |
· · | involving removable or interchangeable coding members, e.g. master tapes, punched cards

|  | G09C 5/00 |
Ciphering apparatus or methods not provided for in the preceding groups, e.g. involving the concealment or deformation of graphic data such as designs, written or printed messages