G
SECTION G — PHYSICS
 G

Note(s)

  1. 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).
  2. 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 G01 and "control" and "regulation" in class G05.
  3. 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 (G09), for enabling the result of a measurement to be known (G01), for signalling the information to a distant point or for giving information which has been signalled from a distant point (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 (G01L) or about some other condition linked to the pressure (another subclass of class G01, e.g., G01K for temperature), to make a record of the pressure or of its occurrence (G07C), to give an alarm (G08B), or to control another apparatus (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
 G08
SIGNALLING (indicating or display devices per se G09F; transmission of pictures H04N)
 G08C
TRANSMISSION SYSTEMS FOR MEASURED VALUES, CONTROL OR SIMILAR SIGNALS (fluid pressure transmission systems F15B; sensing members for specific physical variables, see the relevant subclasses, e.g. of G01, of H01; indicators or recorders, see the relevant subclasses, e.g. G01D, G09F; mechanical means for transferring the output of a sensing member into a different variable G01D 5/00; self-balancing bridges G01R; position control in general G05D 3/00; mechanical control systems G05G; systems for transmitting "on/off" signals only, systems for transmitting alarm conditions G08B; order telegraph systems G08B 9/00; generating electric pulses H03K; coding, decoding or code conversion, in general H03M; transmission of digital information H04L; selective calling from one station to another H04Q 9/00)  [4]
 G08C
Subclass index
TRANSMISSION SYSTEMS IN GENERAL
Electric; non-electric 19/00; 23/00
SYSTEMS FOR TRANSMITTING THE POSITION OF AN OBJECT 21/00
ARRANGEMENTS CHARACTERISED BY THE METHOD OF TRANSMISSION
Multiplex; use of a wireless electrical link 15/00; 17/00
PROCESSING SIGNALS
Differentiating, delaying 13/00
MONITORING, PREVENTING OR CORRECTING ERRORS 25/00
P:10 G08C 13/00
Arrangements for influencing the relationship between signals at input and output, e.g. differentiating, delaying (transferring the output of a sensing member to measuring arrangements giving results not yielding momentary value G01D 1/00; systems for control of position involving comparison between actual and desired values G05D 3/00; computing in general G06)
P:20 G08C 15/00
Arrangements characterised by the use of multiplexing for the transmission of a plurality of signals over a common path (multiplex transmission in general H04J)
P:50 G08C 17/00
Arrangements for transmitting signals characterised by the use of a wireless electrical link  [6]
P:60 G08C 19/00
Electric signal transmission systems (G08C 17/00 takes precedence)
 G08C 19/02
·  in which the signal transmitted is magnitude of current or voltage (G08C 19/36, G08C 19/38 take precedence)
 G08C 19/12
·  in which the signal transmitted is frequency or phase of ac
 G08C 19/16
·  in which transmission is by pulses
 G08C 19/30
·  in which transmission is by selection of one or more conductors or channels from a plurality of conductors or channels (G08C 19/38 takes precedence)
 G08C 19/36
·  using optical means to convert the input signal (analogue/digital conversion per se H03M 1/00)
 G08C 19/38
·  using dynamo-electric devices (operated by pulses G08C 19/16; dynamo-electric machines per se H02K)
P:30 G08C 21/00
Systems for transmitting the position of an object with respect to a predetermined reference system, e.g. tele-autographic system (converting the pattern of mechanical parameters, e.g. force or presence, into electrical signals G06K 11/00)  [5]
P:40 G08C 23/00
Non-electric signal transmission systems, e.g. optical systems
P:0 G08C 25/00
Arrangements for preventing or correcting errors; Monitoring arrangements