|  | H |
SECTION H — ELECTRICITY

|  | H04 |
ELECTRIC COMMUNICATION TECHNIQUE

|  | H04B |
TRANSMISSION (broadcast communication Fulltext... Hierarchy... Expanded...H04H; multiplex systems Fulltext... Hierarchy... Expanded...H04J; secret communication Fulltext... Hierarchy... Expanded...H04K)

|  | H04B |
Note(s) This sub-class deals with the transmission of information-carrying signals, the transmission being independent of the nature of the information, and includes monitoring and testing arrangements and the suppression and limitation of noise and interference.

|  | H04H |
BROADCAST COMMUNICATION (transmission in general Fulltext... Hierarchy... Expanded...H04B; multiplex communication Fulltext... Hierarchy... Expanded...H04J)

|  | H04H |
Note(s) This sub-class deals with (a) the distribution of entertainment or informative matter simultaneously to a number of receiving stations over transmission lines or over radio waves, and (b) the recording of the use made of the broadcast service.

|  | H04J |
MULTIPLEX COMMUNICATION (transmission in general Fulltext... Hierarchy... Expanded...H04B; peculiar to telegraphic communication Fulltext... Hierarchy... Expanded...H04L 5/00; systems for transmitting television signals simultaneously or sequentially Fulltext... Hierarchy... Expanded...H04N 7/08; in exchanges Fulltext... Hierarchy... Expanded...H04Q 11/00)

|  | H04J |
Note(s) This sub-class deals with (a) circuits or apparatus for combining or dividing signals for the purpose of transmitting them simultaneously or sequentially over the same transmission path, and (b) monitoring arrangements therefor.

|  | H04K |
SECRET COMMUNICATION; JAMMING OF COMMUNICATION

|  | H04K |
Note(s) The term "secret communication" includes secret line and radiation transmission systems, i.e. those in which apparatus at the transmitting station modifies the signal in such a way that the information cannot be intelligibly received without corresponding modifying apparatus at the receiving station.

|  | H04L |
TELEGRAPHIC COMMUNICATION (typewriters Fulltext... Hierarchy... Expanded...B41J; order telegraphs, fire or police telegraphs, writing telegraphy, visual telegraphy Fulltext... Hierarchy... Expanded...G08; arrangements common to telegraphic and telephonic communication Fulltext... Hierarchy... Expanded...H04M; selecting Fulltext... Hierarchy... Expanded...H04Q)

|  | H04L |
Note(s) This sub-class deals with systems or apparatus for telegraphic or other data transmission and includes arrangements for teaching telegraphy and for monitoring.

|  | H04M |
TELEPHONIC COMMUNICATION (counting mechanisms Fulltext... Hierarchy... Expanded...G06M; circuits for controlling other apparatus via a telephone cable and not involving telephone switching apparatus Fulltext... Hierarchy... Expanded...G08; reels or other take-up devices for cords Fulltext... Hierarchy... Expanded...H02G 11/00; multiplex transmission between switching centres Fulltext... Hierarchy... Expanded...H04J; selecting arrangements Fulltext... Hierarchy... Expanded...H04Q; transducers Fulltext... Hierarchy... Expanded...H04R)

|  | H04M |
Note(s) This sub-class includes (a) telephonic communication systems combined with other electrical systems, and (b) testing arrangements peculiar to telephonic communication systems. In this sub-class: "Subscriber" is a general term for terminal equipment, e.g. telephone for public use. "Substation" means a subscriber of monitoring equipment which may connect a single subscriber to a line without choice as to subscriber. A "satellite" is a type of exchange the operation of which depends upon control signals received from a supervisory exchange. "Switching centres" includes exchanges and satellites.

|  | H04N |
PICTORIAL COMMUNICATION; TELEVISION (measuring, testing Fulltext... Hierarchy... Expanded...G01; systems for autographic writing, e.g. writing telegraphy, which involve following an outline Fulltext... Hierarchy... Expanded...G08; transferring signals by relative movement between a record track and a transducer Fulltext... Hierarchy... Expanded...G11B; broadcast distribution and the recording of use made thereof Fulltext... Hierarchy... Expanded...H04H)

|  | H04N |
Note(s) This sub-class deals with the transmission of pictures or their transient or permanent reproduction either locally or remotely, by methods involving both the following steps: Step (a): the scanning of a picture, i.e. the analysis of the whole of a picture-containing area by resolving it into an area or a plurality of areas of which at least one of the two dimensions is elemental, simultaneously or in a sequence, and the derivation in response thereto of a picture-representative electric signal; Step (b): the reproduction of the whole of a picture-containing area by the reproduction in response to a picture-representative electric signal of an area or a plurality of areas of which at least one of the two dimensions is elemental, simultaneously or in sequence. In this sub-class, "pictorial communication systems" are those systems for the transmission and reproduction of arbitrarily composed pictures in which the local light variations composing a picture are not subject to variation with time, e.g. documents (both written and printed), maps, charts, photographs (other than cinematograph films). In this sub-class, "television systems" are those systems for the transmission and reproduction of arbitrarily composed pictures in which the local light variations composing a picture may change with time, e.g. natural "live" scenes, recordings of such scenes such as cinematograph films. This sub-class includes circuits specially designed for dealing with television or pictorial communication signals, as distinct from merely signals of a particular frequency range. This sub-class does not include the following subject matter: Circuits or other parts of systems which form the subject of other sub-classes, which are dealt with in the corresponding sub-classes, e.g. Fulltext... Hierarchy... Expanded...H03C, Fulltext... Hierarchy... Expanded...H03F, Fulltext... Hierarchy... Expanded...H04B, Fulltext... Hierarchy... Expanded...H04H. Systems in which legible alphanumeric or like character forms are analysed according to Step (a) to derive an electric signal from which the character is recognised by comparison with stored information, which are dealt with in Fulltext... Hierarchy... Expanded...G06K. Systems for the direct photographic copying of an original picture in which an electric signal representative of the picture is derived according to Step (a) and employed to modify the operation of the system, which are dealt with in Fulltext... Hierarchy... Expanded...G03. Systems for the reproduction according to Step (b) of pictures comprising alphanumeric or like character forms but involving the production of the equivalent of a signal which would be derived by Step (a), e.g. by cams, punched card or tape, coded control signal, or other means, which are dealt with in the sub-class for the application, e.g. Fulltext... Hierarchy... Expanded...G01D, Fulltext... Hierarchy... Expanded...G06F, Fulltext... Hierarchy... Expanded...H04L. Systems involving Step (a) or Step (b) for producing (1) engraved, indented, apertured, or otherwise formed printing surfaces, or (2) photographs specially arranged for producing such printing surfaces or for use generally in printing or duplication, which are dealt with in Fulltext... Hierarchy... Expanded...G03F. Systems involving Step (a) or Step (b) but otherwise specially modified for printing or duplication, which are dealt with in such sub-classes as Fulltext... Hierarchy... Expanded...B41M, Fulltext... Hierarchy... Expanded...G03C, Fulltext... Hierarchy... Expanded...G03F. Systems for the reproduction according to Step (b) of pictures comprising alphanumeric or like character forms and involving the generation according to Step (a) of picture-representative electric signals from a pre-arranged assembly of such characters, or records thereof, forming an integral part of the systems, are dealt with in the sub-class for the application, e.g. Fulltext... Hierarchy... Expanded...G06K, Fulltext... Hierarchy... Expanded...H04N.

|  | H04Q |
SELECTING (switches, relays, selectors Fulltext... Hierarchy... Expanded...H01H)

|  | H04Q |
Note(s) This sub-class deals with methods, circuits, or apparatus for establishing selectively a connection between a desired number of stations (normally two), or between a main station and a desired number of substations (normally one) for the purpose of transferring information via this connection after it has been established. The sub-class also deals with selective calling arrangements over connections already established. In either case, the connection may be by means of electric conductors or electromagnetic waves. In this sub-class: "Subscriber" is a general term for terminal equipment, e.g. telephone for public use. "Substation" means a subscriber or monitoring equipment which may connect a single subscriber to a line without choice as to subscriber. A "satellite" is a kind of exchange the operation of which depends upon control signals received from a supervisory exchange. "Switching centres" include exchanges and satellites.

|  | H04R |
ELECTROMECHANICAL TRANSDUCERS (for performing mechanical work Fulltext... Hierarchy... Expanded...B06B; use of transducers as sensing elements for measuring Fulltext... Hierarchy... Expanded...G01, Fulltext... Hierarchy... Expanded...G04; construction or circuits of vibrators whose output is of frequency unrelated to that of the electric supply Fulltext... Hierarchy... Expanded...G10K; recording or reproducing heads incorporating transducers Fulltext... Hierarchy... Expanded...G11B; dynamo-electric machines Fulltext... Hierarchy... Expanded...H02K)

|  | H04R |
Note(s) This sub-class deals with (a) instruments capable of converting sound, ultrasonic, or infrasonic waves, or other mechanical vibrations into variations of electric current or voltage or vice versa, (b) instruments actuated by variations of electric current or voltage for cutting grooves in records, (c) circuits for the instruments of (a) and (b), (d) deaf-aid sets, (e) public address systems, and (f) monitoring or testing the equipment of (a) to (e).