H
SECTION H — ELECTRICITY
 H04
ELECTRIC COMMUNICATION TECHNIQUE
 H04L
TELEGRAPHIC COMMUNICATION (typewriters B41J; order telegraphs, fire or police telegraphs, writing telegraphy, visual telegraphy G08B; arrangements common to telegraphic and telephonic communication H04M; selecting 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.

 H04L 1/00
Arrangements for detecting or preventing errors in the information received (correcting synchronisation H04L 7/00; arrangements in the transmission path H04B)
 H04L 1/02
·  by diversity reception (in general H04B 7/02)
 H04L 1/04
·  ·  using frequency diversity
 H04L 1/06
·  ·  using space diversity
 H04L 1/08
·  by repeating transmission, e.g. Verdan system
 H04L 1/10
·  by using codes designed for error detection with or without automatic error correction, e.g. using Hamming code, using parity-checking
 H04L 1/12
·  by using return channel
 H04L 1/14
·  ·  in which the signals are sent back to the transmitter to be checked
 H04L 1/16
·  ·  in which the return channel carries supervisory signals, e.g. repetition request signals
 H04L 1/18
·  ·  ·  Automatic repetition systems, e.g. van Duuren system
 H04L 3/00
Arrangements for converting one code into another code (code conversion in general H03K 13/24)
 H04L 3/02
·  Arrangements for converting codes in which each character is represented by the same number of equal-length code elements into error-detecting or error-correcting codes, or vice versa, e.g. five-unit code into seven-unit code with three marking and four spacing elements
 H04L 3/04
·  Arrangements for converting codes in which each character is represented by the same number of equal-length code elements into dot-and-dash codes or vice versa
 H04L 5/00
Arrangements affording multiple use of the transmission path (multiplex communication in general H04J)
 H04L 5/02
·  Channels characterised by the type of signal
 H04L 5/04
·  ·  the signals being represented by different amplitudes or polarities, e.g. quadriplex
 H04L 5/06
·  ·  the signals being represented by different frequencies (combined with time-division multiplexing H04L 5/26)
 H04L 5/08
·  ·  ·  each combination of signals in different channels being represented by a predetermined frequency
 H04L 5/10
·  ·  ·  with dynamo-electric generation of carriers; with mechanical filters or demodulators
 H04L 5/12
·  ·  the signals being represented by different phase modulations of a single carrier
 H04L 5/14
·  Two-way operation using the same type of signal, i.e. duplex (conditioning for two-way transmission in general H04B 3/20)
 H04L 5/16
·  ·  Half-duplex systems; Simplex-duplex switching; Transmission of break signals
 H04L 5/18
·  ·  Automatic changing of the traffic direction
 H04L 5/20
·  using different combinations of lines, e.g. phantom working
 H04L 5/22
·  using time-division multiplexing
 H04L 5/24
·  ·  with start-stop synchronous converters
 H04L 5/26
·  ·  combined with the use of different frequencies
 H04L 7/00
Arrangements for synchronising receiver with transmitter
 H04L 7/02
·  Speed or phase control by the received code signals, the signals containing no special synchronisation information
 H04L 7/04
·  Speed or phase control by synchronisation signals
 H04L 7/06
·  ·  the synchronisation signals differing from the information signals in amplitude, polarity, or frequency
 H04L 7/08
·  ·  the synchronisation signals recurring cyclically
 H04L 7/10
·  ·  Arrangements for initial synchronisation
 H04L 9/00
Arrangements for secret communication (in general H04K)
 H04L 9/02
·  by adding a key-signal to make the desired signal unintelligible
 H04L 9/04
·  ·  Arrangements for generating key-code characters
 H04L 11/00
Exchanges; Connections between exchanges; Connections between exchanges and substations
 H04L 11/02
·  Details
 H04L 11/04
·  ·  Switch-boards
 H04L 11/06
·  ·  Answer-back mechanisms or circuits
 H04L 11/08
·  ·  Monitoring arrangements
 H04L 11/10
·  ·  Allotting numbers to messages; Counting characters, words, or messages (counting in general G06M)
 H04L 11/12
·  ·  Testing equipment; Routine testing
 H04L 11/14
·  ·  Current supply arrangements
 H04L 11/15
·  ·  Arrangements for remote connection or disconnection of substations or of equipment thereat
 H04L 11/16
·  Party-line systems
 H04L 11/18
·  Systems affording broadcast facilities; Systems affording conference facilities
 H04L 11/20
·  Message switching systems (permutation-code selecting H04Q 3/02)
 H04L 11/22
·  ·  Manual relay systems, e.g. push-button switching
 H04L 11/24
·  ·  ·  with perforated tape storage
 H04L 13/00
Details of the apparatus or circuits covered by groups H04L 15/00 and H04L 17/00
 H04L 13/02
·  Details not particular to receiver or transmitter
 H04L 13/04
·  ·  Driving mechanisms; Clutches (in general F16)
 H04L 13/06
·  ·  Tape or page guiding or feeding devices
 H04L 13/08
·  ·  Intermediate storage means
 H04L 13/10
·  ·  Distributors
 H04L 13/12
·  ·  ·  Non-mechanical distributors, e.g. relay distributors
 H04L 13/14
·  ·  ·  ·  Electronic distributors (in general H 03 K 17/40)
 H04L 13/16
·  of transmitters, e.g. code-bars, code-discs
 H04L 13/18
·  of receivers
 H04L 15/00
Apparatus or local circuits for transmitting or receiving dot-and-dash codes, e.g. Morse code (telegraph tapping keys H01H 21/86)
 H04L 15/02
·  Teaching apparatus; Keys structurally combined with sound generators
 H04L 15/04
·  Apparatus or circuits at the transmitting end
 H04L 15/06
·  ·  with a restricted number of keys, e.g. separate key for each type of code element
 H04L 15/08
·  ·  ·  with a single key which transmits dots in one position and dashes in a second position
 H04L 15/10
·  ·  ·  combined with perforating apparatus
 H04L 15/12
·  ·  with keyboard co-operating with code-bars
 H04L 15/14
·  ·  ·  combined with perforating apparatus
 H04L 15/16
·  ·  with keyboard co-operating with code discs
 H04L 15/18
·  ·  Automatic transmitters, e.g. controlled by perforated tape
 H04L 15/20
·  ·  ·  with optical sensing means
 H04L 15/22
·  ·  Apparatus or circuits for sending one or a restricted number of signals, e.g. distress signals
 H04L 15/24
·  Apparatus or circuits at the receiving end
 H04L 15/26
·  ·  Operating only on reception of predetermined code signals, e.g. distress signals, party-line call signals
 H04L 15/28
·  ·  Code reproducing apparatus
 H04L 15/30
·  ·  ·  Writing recorders
 H04L 15/32
·  ·  ·  Perforating recorders
 H04L 15/34
·  ·  Apparatus for recording received coded signals after translation, e.g. as type-characters
 H04L 17/00
Apparatus or local circuits for transmitting or receiving codes wherein each character is represented by the same number of equal-length code elements, e.g. Baudot code
 H04L 17/02
·  Apparatus or circuits at the transmitting end
 H04L 17/04
·  ·  with keyboard co-operating with code-bars
 H04L 17/06
·  ·  ·  Contact operating means
 H04L 17/08
·  ·  ·  combined with perforating apparatus
 H04L 17/10
·  ·  with keyboard co-operating with code-discs
 H04L 17/12
·  ·  Automatic transmitters, e.g. controlled by perforated tape
 H04L 17/14
·  ·  ·  with optical sensing means
 H04L 17/16
·  Apparatus or circuits at the receiving end
 H04L 17/18
·  ·  Code selection mechanisms
 H04L 17/20
·  ·  using perforating recorders
 H04L 17/22
·  ·  using mechanical translation and type-bar printing
 H04L 17/24
·  ·  using mechanical translation and type-head printing, e.g. type-wheel, type-cylinder
 H04L 17/26
·  ·  using aggregate motion translation
 H04L 17/28
·  ·  using pneumatic or hydraulic translation
 H04L 17/30
·  ·  using electric or electronic translation
 H04L 19/00
Apparatus or local circuits for step-by-step systems
 H04L 21/00
Apparatus or local circuits for mosaic printer telegraph systems
 H04L 21/02
·  at the transmitting end
 H04L 21/04
·  at the receiving end
 H04L 23/00
Apparatus or local circuits for systems other than those covered by groups H04L 15/00-H04L 21/00
 H04L 25/00
Direct-current systems
 H04L 25/02
·  Details (circuits in general for handling pulses H03K; in line transmission systems in general H04B 3/02)
 H04L 25/04
·  ·  Passive shaping networks in transmitter or receiver
 H04L 25/06
·  ·  Dc level restoring means; Bias distortion correction
 H04L 25/08
·  ·  Modifications for reducing interference; Modifications for reducing effects due to line faults
 H04L 25/10
·  ·  Compensating for variations in line balance
 H04L 25/12
·  ·  Compensating for variations in line impedance
 H04L 25/14
·  ·  Channel dividing arrangements
 H04L 25/16
·  ·  Interpolating arrangements e.g. earthing of line between pulses
 H04L 25/18
·  ·  Arrangements for inductively generating telegraphic signals (induction coil interrupters H01H 51/34; dynamo-electric generators H02K)
 H04L 25/20
·  ·  Repeater circuits; Relay circuits
 H04L 25/22
·  ·  ·  Repeaters for converting two wires to four wires (in general H04B); Repeaters for converting single current to double current
 H04L 25/24
·  ·  ·  Relay circuits using discharge tubes or semiconductor devices
 H04L 25/26
·  ·  ·  Circuits with optical sensing means
 H04L 25/28
·  ·  ·  Repeaters using modulation and subsequent demodulation
 H04L 25/30
·  Non-synchronous systems
 H04L 25/32
·  ·  characterised by the code employed
 H04L 25/34
·  ·  ·  using three or more different amplitudes, e.g. cable code
 H04L 25/36
·  ·  with electric or magnetic storage of the signals before transmitting or receiving to increase transmission speed
 H04L 25/38
·  Synchronous or start-stop systems, e.g. for Baudot code
 H04L 25/40
·  ·  Transmitting circuits; Receiving circuits (repeater circuits, relay circuits H04L 25/52)
 H04L 25/42
·  ·  ·  using mechanical distributors
 H04L 25/44
·  ·  ·  using relay distributors
 H04L 25/46
·  ·  ·  using tuning forks or vibrating reeds
 H04L 25/48
·  ·  ·  characterised by the code employed
 H04L 25/50
·  ·  ·  with electric or magnetic storage of the signals before transmitting or receiving to increase transmission speed
 H04L 25/52
·  ·  Repeater circuits; Relay circuits
 H04L 25/54
·  ·  ·  using mechanical distributors
 H04L 25/56
·  ·  ·  Non-electrical regenerative repeaters
 H04L 25/58
·  ·  ·  using relay distributors
 H04L 25/60
·  ·  ·  Regenerative repeaters with electromagnetic switches
 H04L 25/62
·  ·  ·  using tuning forks or vibrating reeds
 H04L 25/64
·  ·  ·  Start-stop regenerative repeaters using discharge tubes or semiconductor devices
 H04L 25/66
·  ·  ·  Synchronous repeaters using discharge tubes or semiconductor devices
 H04L 27/00
Alternating-current systems
 H04L 27/02
·  Amplitude-modulated carrier systems, e.g. using on/off keying
 H04L 27/04
·  ·  Modulator circuits (in general H03C); Transmitter circuits
 H04L 27/06
·  ·  Demodulator circuits (in general H03D); Receiver circuits
 H04L 27/08
·  ·  Amplitude regulation arrangements
 H04L 27/10
·  Frequency-modulated carrier systems, i.e. using frequency-shift keying
 H04L 27/12
·  ·  Modulator circuits (in general H03C); Transmitter circuits
 H04L 27/14
·  ·  Demodulator circuits (in general H03D); Receiver circuits
 H04L 27/16
·  ·  Frequency regulation arrangements
 H04L 27/18
·  Phase-modulated carrier systems, i.e. using phase-shift keying
 H04L 27/20
·  ·  Modulator circuits (in general H03C); Transmitter circuits
 H04L 27/22
·  ·  Demodulator circuits (in general H03D); Receiver circuits
 H04L 27/24
·  ·  Half-wave signalling systems
 H04L 27/26
·  Systems using multi-frequency codes
 H04L 27/28
·  ·  with simultaneous transmission of different frequencies each representing one code element
 H04L 27/30
·  ·  wherein each code element is represented by a combination of frequencies