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.
to yield a signal which is a function of two or more signals, e.g. sum, product
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 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
P:50
G08C 17/00
Arrangements for transmitting signals characterised by the use of a wireless electrical link [6]
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)
being of the type with a three-phase stator and a rotor fed by constant-frequency ac, e.g. selsyn, magslip
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 Fulltext... Hierarchy... Expanded...G06K 11/00) [5]
P:40
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]
P:0
G08C 25/00
Arrangements for preventing or correcting errors; Monitoring arrangements
G08C 25/02
·
by signalling back from receiving station to transmitting station