IPC 6 English version H04L !A-H04L 12/66

H04L-H04L01266

SECTION H– ELECTRICITY

H 04

ELECTRIC COMMUNICATION TECHNIQUE

H 04 L

TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (typewriters B 41 J; order telegraphs, fire or police telegraphs G 08 B; visual telegraphy G 08 B, G 08 C; teleautographic systems G 08 C; ciphering or deciphering apparatus per se G 09 C; coding, decoding or code conversion, in general H 03 M; arrangements common to telegraphic and telephonic communication H 04 M; selecting H 04 Q) [4]

Note

This subclass covers transmission of signals having been supplied in digital form and includes data transmission, telegraphic communication, or methods or arrangements for monitoring.

Arrangements for detecting or preventing errors in the information received (correcting synchronisation H 04 L 7/00; arrangements in the transmission path H 04 B)

by diversity reception (in general H 04 B 7/02)

using frequency diversity

using space diversity

by repeating transmission, e.g. Verdan system

by using return channel

in which the signals are sent back to the transmitter to be checked

in which the return channel carries supervisory signals, e.g. repetition request signals

Automatic repetition systems, e.g. van Duuren system

using signal-quality detector [3]

using redundant apparatus to increase reliability [3]

Testing correct operation [3]

Arrangements affording multiple use of the transmission path (multiplex communication in general H 04 J)

Channels characterised by the type of signal

the signals being represented by different amplitudes or polarities, e.g. quadriplex

the signals being represented by different frequencies (combined with time-division multiplexing H 04 L 5/26)

each combination of signals in different channels being represented by a fixed frequency

with dynamo-electric generation of carriers; with mechanical filters or demodulators

the signals being represented by different phase modulations of a single carrier

Two-way operation using the same type of signal, i.e. duplex (conditioning for two-way transmission in general H 04 B 3/20)

Half-duplex systems; Simplex/duplex switching; Transmission of break signals

Automatic changing of the traffic direction

using different combinations of lines, e.g. phantom working

using time-division multiplexing

with start-stop synchronous converters

combined with the use of different frequencies

Arrangements for synchronising receiver with transmitter

Speed or phase control by the received code signals, the signals containing no special synchronisation information

027

extracting the synchronising or clock signal from the received signal spectrum, e.g. by using a resonant or bandpass circuit [5]

033

using the transitions of the received signal to control the phase of the synchronising-signal- generating means, e.g. using a phase-locked loop [5]

Speed or phase control by synchronisation signals

the synchronisation signals differing from the information signals in amplitude, polarity, or frequency

the synchronisation signals recurring cyclically

Arrangements for initial synchronisation

Note

In group H 04 L 9/00 to H 04 L 9/32, in the absence of an indication to the contrary, classification is made in the last appropriate place. [5]

Arrangements for secret or secure communication (spread spectrum techniques in general H 04 B 1/69)

the encryption apparatus using shift registers or memories for blockwise coding, e.g. D.E.S. systems [5]

Key distribution [5]

with particular housing, physical features or manual controls [5]

Transmitting and receiving encryption devices synchronised or initially set up in a particular manner [5]

using a plurality of keys or algorithms [5]

the keys or algorithms being changed during operation [5]

Encryption by serially and continuously modifying data stream elements, e.g. stream cipher systems [5]

Pseudorandom key sequence combined element-for-element with data sequence [5]

with particular pseudorandom sequence generator [5]

sequence produced by more than one generator [5]

producing a nonlinear pseudorandom sequence [5]

using particular encryption algorithm [5]

Public key, i.e. encryption algorithm being computationally infeasible to invert and users' encryption keys not requiring secrecy [5]

including means for verifying the identity or authority of a user of the system (computer systems G 06 F; coin-freed or like apparatus with coded identity card or credit card G 07 F 7/08) [5]

Bits, or blocks of bits, of the telegraphic message being interchanged in time [5]

with means for detecting characters not meant for transmission [5]

Encryption being effected by mechanical apparatus, e.g. rotating cams, switches, keytape punchers [5]

12/

Data switching networks (interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units G 06 F 13/00) [5]

12/

Details [5]

12/

Switchboards [5]

12/

Answer-back mechanisms or circuits [5]

12/

Alloting numbers to messages; Counting characters, words or messages [5]

12/

Current supply arrangements [5]

12/

Arrangements for remote connection or disconnection of substations or of equipment thereof [5]

12/

Charging arrangements [5]

12/

Arrangements for providing special services to substations [5]

12/

for broadcast or conference [5]

12/

for converting transmission speed from the inherent speed of a substation to the inherent speed of other substations [5]

12/

Arrangements for preventing the taking of data from a data transmission channel without authorisation (means for verifying the identity or the authority of a user of a secure or secret communication system H 04 L 9/32) [5]

12/

Arrangements for maintenance or administration [5]

12/

Monitoring arrangements; Testing arrangements [5]

12/

characterised by path configuration, e.g. local area networks (LAN), wide area networks (WAN) [5,6]

12/

Bus networks [5,6]

12/

403

with centralised control, e.g. polling [6]

12/

407

with decentralised control [6]

12/

413

with random access, e.g. carrier-sense multiple-access with collision detection (CSMA-CD) [6]

12/

417

with deterministic access, e.g. token passing [6]

12/

Loop networks [5,6]

12/

423

with centralised control, e.g. polling [6]

12/

427

with decentralised control [6]

12/

with synchronous transmission, e.g. time division multiplex (TDM), slotted rings [6]

12/

433

with asynchronous transmission, e.g. token ring, register insertion [6]

12/

437

Ring fault isolation or reconfiguration [6]

12/

Star or tree networks [5,6]

12/

Interconnection of networks [5,6]

12/

(transferred to H 04 L 12/28)

12/

Circuit switching systems, i.e. systems in which the path is physically permanent during the communication [5,6]

12/

using time division techniques (in digital transmission systems H 04 L 5/22) [5,6]

12/

Stored and forward switching systems [5,6]

12/

Packet switching systems [5,6]

12/

Message switching systems (permutation- code selecting H 04 Q 3/02) [5,6]

12/

Manual relay systems, e.g. push-button switching [5,6]

12/

with perforated tape storage [5,6]

12/

Hybrid switching systems [5,6]

12/

Arrangements for connecting between networks having differing types of switching systems, e.g. gateways [5,6]

H04L 13/00 - H04L 29/14