|  | 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

|  | G08 |
SIGNALLING (indicating or display devices per se Fulltext... Hierarchy... Expanded...G09F; transmission of pictures Fulltext... Hierarchy... Expanded...H04N)

|  | G08C |
TRANSMISSION SYSTEMS FOR MEASURED VALUES, CONTROL OR SIMILAR SIGNALS (fluid pressure transmission systems Fulltext... Hierarchy... Expanded...F15B; sensing members for specific physical variables, see the relevant subclasses, e.g. of Fulltext... Hierarchy... Expanded...G01, of Fulltext... Hierarchy... Expanded...H01; indicators or recorders, see the relevant subclasses, e.g. Fulltext... Hierarchy... Expanded...G01D, Fulltext... Hierarchy... Expanded...G09F; mechanical means for transferring the output of a sensing member into a different variable Fulltext... Hierarchy... Expanded...G01D 5/00; self-balancing bridges Fulltext... Hierarchy... Expanded...G01R; position control in general Fulltext... Hierarchy... Expanded...G05D 3/00; mechanical control systems Fulltext... Hierarchy... Expanded...G05G; systems for transmitting "on/off" signals only, systems for transmitting alarm conditions Fulltext... Hierarchy... Expanded...G08B; order telegraph systems Fulltext... Hierarchy... Expanded...G08B 9/00; generating electric pulses Fulltext... Hierarchy... Expanded...H03K; coding, decoding or code conversion, in general Fulltext... Hierarchy... Expanded...H03M; transmission of digital information Fulltext... Hierarchy... Expanded...H04L; selective calling from one station to another Fulltext... Hierarchy... Expanded...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

|  | 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 Fulltext... Hierarchy... Expanded...G01D 1/00; systems for control of position involving comparison between actual and desired values Fulltext... Hierarchy... Expanded...G05D 3/00; computing in general Fulltext... Hierarchy... Expanded...G06)

|  | G08C 13/02 |
· | to yield a signal which is a function of two or more signals, e.g. sum, product

|  | 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 Fulltext... Hierarchy... Expanded...H04J)

|  | G08C 15/02 |
· | simultaneously, i.e. using frequency division

|  | G08C 15/04 |
· · | the signals being modulated on carrier frequencies

|  | G08C 15/06 |
· | successively, i.e. using time division

|  | G08C 15/08 |
· · | the signals being represented by amplitude of current or voltage in transmission link

|  | G08C 15/10 |
· · | the signals being represented by frequencies or phase of current or voltage in transmission link

|  | G08C 15/12 |
· · | the signals being represented by pulse characteristics in transmission link

|  | G08C 17/00 |
Arrangements for transmitting signals characterised by the use of a wireless electrical link [6]

|  | G08C 17/02 |
· | using a radio link [6]

|  | G08C 17/04 |
· | using magnetically coupled devices [6]

|  | G08C 17/06 |
· | using capacity coupling [6]

|  | G08C 19/00 |
Electric signal transmission systems (Fulltext... Hierarchy... Expanded...G08C 17/00 takes precedence)

|  | G08C 19/02 |
· | in which the signal transmitted is magnitude of current or voltage (Fulltext... Hierarchy... Expanded...G08C 19/36, Fulltext... Hierarchy... Expanded...G08C 19/38 take precedence)

|  | G08C 19/04 |
· · | using variable resistance

|  | G08C 19/06 |
· · | using variable inductance

|  | G08C 19/08 |
· · · | differentially influencing two coils

|  | G08C 19/10 |
· · | using variable capacitance

|  | G08C 19/12 |
· | in which the signal transmitted is frequency or phase of ac

|  | G08C 19/14 |
· · | using combination of fixed frequencies

|  | G08C 19/16 |
· | in which transmission is by pulses

|  | G08C 19/18 |
· · | using a variable number of pulses in a train

|  | G08C 19/20 |
· · · | operating on dynamo-electric devices, e.g. step motor

|  | G08C 19/22 |
· · | by varying the duration of individual pulses

|  | G08C 19/24 |
· · | using time shift of pulses

|  | G08C 19/26 |
· · | by varying pulse repetition frequency

|  | G08C 19/28 |
· · | using pulse code

|  | G08C 19/30 |
· | in which transmission is by selection of one or more conductors or channels from a plurality of conductors or channels (Fulltext... Hierarchy... Expanded...G08C 19/38 takes precedence)

|  | G08C 19/32 |
· · | of one conductor or channel

|  | G08C 19/34 |
· · | of a combination of conductors or channels

|  | G08C 19/36 |
· | using optical means to convert the input signal (analogue/digital conversion per se Fulltext... Hierarchy... Expanded...H03M 1/00)

|  | G08C 19/38 |
· | using dynamo-electric devices (operated by pulses Fulltext... Hierarchy... Expanded...G08C 19/20; dynamo-electric machines per se Fulltext... Hierarchy... Expanded...H02K)

|  | G08C 19/40 |
· · | of which only the rotor or the stator carries a winding to which a signal is applied, e.g. using step motor

|  | G08C 19/42 |
· · · | having three stator poles

|  | G08C 19/44 |
· · · | having more than three stator poles

|  | G08C 19/46 |
· · | of which both rotor and stator carry windings (having squirrel-cage rotor Fulltext... Hierarchy... Expanded...G08C 19/40)

|  | G08C 19/48 |
· · · | being of the type with a three-phase stator and a rotor fed by constant-frequency ac, e.g. selsyn, magslip

|  | 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 Fulltext... Hierarchy... Expanded...G06K 11/00) [5]

|  | G08C 23/00 |
Non-electric signal transmission systems, e.g. optical systems

|  | G08C 23/02 |
· | using acoustic waves [6]

|  | G08C 23/04 |
· | using light waves, e.g. infra-red [6]

|  | G08C 23/06 |
· · | through light guides, e.g. optical fibres [6]

|  | G08C 25/00 |
Arrangements for preventing or correcting errors; Monitoring arrangements

|  | G08C 25/02 |
· | by signalling back from receiving station to transmitting station

|  | G08C 25/04 |
· | by recording transmitted signals