|  | H |
SECTION H — ELECTRICITY

|  | H04 |
ELECTRIC COMMUNICATION TECHNIQUE

|  | 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" include exchanges and satellites.

|  | H04M 1/00 |
Substation equipment, e.g. for use by subscribers; Analogous equipment at exchanges (prepayment telephone coin boxes Fulltext... Hierarchy... Expanded...H04M 17/00; current supply arrangements Fulltext... Hierarchy... Expanded...H04M 19/00)

|  | H04M 1/02 |
· | Constructional features of telephone sets

|  | H04M 1/03 |
· · | Constructional features of telephone transmitters or receivers, e.g. telephone hand-sets (transducers in general Fulltext... Hierarchy... Expanded...H04R 1/00) [2]

|  | H04M 1/04 |
· · | Supports for telephone transmitters or receivers (for transducers in general Fulltext... Hierarchy... Expanded...H04R 1/00)

|  | H04M 1/05 |
· · · | adapted for use on head, throat, or breast

|  | H04M 1/06 |
· · · | Hooks; Cradles

|  | H04M 1/08 |
· · · · | associated with switches operated by weight of receiver or hand-set

|  | H04M 1/10 |
· · · · | associated with switches operated by magnetic effect due to proximity of receiver or hand-set

|  | H04M 1/11 |
· · | Supports for sets, e.g. incorporating armrests

|  | H04M 1/12 |
· · · | Adjustable supports, e.g. extensible

|  | H04M 1/13 |
· · · · | pantographic

|  | H04M 1/14 |
· · · | with resilient means to eliminate extraneous vibrations

|  | H04M 1/15 |
· · | Protection of telephone cord; Guiding telephone cord; Winding-up telephone cord (in general Fulltext... Hierarchy... Expanded...H02G 11/00)

|  | H04M 1/17 |
· · | Hygienic or sanitary devices on telephone equipment (for mouthpieces or earpieces per se Fulltext... Hierarchy... Expanded...H04R 1/12) [2]

|  | H04M 1/18 |
· · | Telephone sets modified for use in ships, mines, or other places exposed to adverse environment (Fulltext... Hierarchy... Expanded...H04M 1/19 takes precedence; telephone cabinets per se Fulltext... Hierarchy... Expanded...E04H 1/14)

|  | H04M 1/19 |
· · | Arrangements of transmitters, receivers, or complete sets to prevent eavesdropping, to attenuate local noise or to prevent undesired transmission; Special mouthpieces or receivers therefor (circuit arrangements for preventing eavesdropping Fulltext... Hierarchy... Expanded...H04M 1/68; telephone cabinets per se Fulltext... Hierarchy... Expanded...E04H 1/14)

|  | H04M 1/20 |
· · | Arrangements for preventing acoustic feedback (Fulltext... Hierarchy... Expanded...H04M 1/62 takes precedence)

|  | H04M 1/21 |
· · | Combinations with auxiliary equipment, e.g. with clock, with memoranda pad

|  | H04M 1/22 |
· · | Illuminating; Arrangements for improving visibility of characters on dials

|  | H04M 1/23 |
· · | Construction or mounting of dials or of equivalent devices; Means for facilitating the use thereof (by improving visibility Fulltext... Hierarchy... Expanded...H04M 1/22)

|  | H04M 1/235 |
( transferred to Fulltext... Hierarchy... Expanded...H04M 1/315 )

|  | H04M 1/24 |
· | Arrangements for testing (measuring electric values Fulltext... Hierarchy... Expanded...G01R; testing transducers Fulltext... Hierarchy... Expanded...H04R 29/00)

|  | H04M 1/26 |
· | Devices for calling a subscriber

|  | H04M 1/27 |
· · | Devices whereby a plurality of signals may be stored simultaneously [2]

|  | H04M 1/272 |
· · · | with provision for storing only one subscriber number at a time, e.g. by keyboard or dial [2]

|  | H04M 1/274 |
· · · | with provision for storing more than one subscriber number at a time, e.g. using toothed disc [2]

|  | H04M 1/276 |
· · · · | using magnetic recording, e.g. on tape [2]

|  | H04M 1/278 |
· · · · | using punched cards or tapes [2]

|  | H04M 1/30 |
· · | Devices which can set up and transmit only one digit at a time

|  | H04M 1/31 |
· · · | by interrupting current to generate trains of pulses; by periodically opening and closing contacts to generate trains of pulses [2]

|  | H04M 1/315 |
· · · · | Clutches, spring assemblies, speed regulators, e.g. centrifugal brakes (Fulltext... Hierarchy... Expanded...Fulltext... Hierarchy... Expanded...H04M 1/32-H04M 1/40 take precedence) [3]

|  | H04M 1/32 |
· · · · | Locking setting devices during transmission to prevent interference by user

|  | H04M 1/34 |
· · · · | Lost-motion or other arrangements for ensuring a pause between successive digit transmissions

|  | H04M 1/36 |
· · · · | Preventing the sending of predetermined numbers

|  | H04M 1/38 |
· · · · | Pulses transmitted by a movement variably limited by the setting of a stop

|  | H04M 1/40 |
· · · · | wherein the setting-operation short-circuits or open-circuits the transmitting mechanism during a variable part of a cycle

|  | H04M 1/50 |
· · · | by generating or selecting currents of predetermined frequencies or combinations of frequencies [2]

|  | H04M 1/515 |
· · | by generating or selecting other signals than trains of pulses of similar shape or other signals than currents of one or more different frequencies, e.g. generation of dc signals of alternating polarity, coded pulses, impedance dialling [2]

|  | H04M 1/52 |
· · | Arrangements wherein a dial or equivalent is mechanically coupled to a line selector

|  | H04M 1/53 |
· · | Generation of additional signals, e.g. additional pulses [2]

|  | H04M 1/54 |
· · · | Arrangements wherein a dial or equivalent generates identifying signals, e.g. in party-line systems [2]

|  | H04M 1/56 |
· | Arrangements for indicating or recording the called number at the calling subscriber's set

|  | H04M 1/57 |
· | Arrangements for indicating or recording the number of the calling subscriber at the called subscriber's set (at the operator set in a manual exchange Fulltext... Hierarchy... Expanded...H04M 5/20) [2]

|  | H04M 1/58 |
· | Anti-side-tone circuits (hybrid circuits for carrier-frequency operation Fulltext... Hierarchy... Expanded...H04B 1/00)

|  | H04M 1/60 |
· | including speech amplifiers

|  | H04M 1/62 |
· · | Constructional arrangements

|  | H04M 1/64 |
· | Automatic arrangements for answering calls; Automatic arrangements for recording messages for absent subscribers (centralised dictation systems Fulltext... Hierarchy... Expanded...H04M 11/10)

|  | H04M 1/65 |
· · | Automatic arrangements for recording messages for absent subscribers [2]

|  | H04M 1/66 |
· | with means for preventing unauthorised or fraudulent calling

|  | H04M 1/68 |
· | Circuit arrangements for preventing eavesdropping

|  | H04M 1/70 |
· · | Lock-out or secrecy arrangements in party-line systems

|  | H04M 1/72 |
· | Substation extension arrangements

|  | H04M 1/74 |
· | with means for reducing interference; with means for reducing effects due to line faults

|  | H04M 1/76 |
· | Compensating for differences in line impedance (in general Fulltext... Hierarchy... Expanded...H04B)

|  | H04M 1/78 |
· | Circuit arrangements in which low-frequency speech signals proceed in one direction on the line, while speech signals proceeding in the other direction on the line are modulated on a high-frequency carrier signal (repeater circuits Fulltext... Hierarchy... Expanded...H04B 3/38) [2]

|  | H04M 3/00 |
Automatic or semi-automatic exchanges

|  | H04M 3/02 |
· | Ringing or otherwise calling substations (selective calling Fulltext... Hierarchy... Expanded...H04Q)

|  | H04M 3/04 |
· · | calling signal supplied from final selector

|  | H04M 3/06 |
· · | calling signal supplied from subscriber's line circuit

|  | H04M 3/08 |
· | Indicating faults in circuits or apparatus

|  | H04M 3/10 |
· · | Providing fault- or trouble-signals

|  | H04M 3/12 |
· · | Marking faulty circuits "busy"; Enabling equipment to disengage itself from faulty circuits

|  | H04M 3/14 |
· · | Signalling existence of persistent "off-hook" condition

|  | H04M 3/16 |
· | with lock-out or secrecy provision in party-line systems

|  | H04M 3/18 |
· | with means for reducing interference; with means for reducing effects due to line faults

|  | H04M 3/20 |
· | with means for interrupting existing connections; with means for breaking-in on conversations

|  | H04M 3/22 |
· | Supervisory, monitoring, or testing arrangements

|  | H04M 3/24 |
· · | with provision for checking the normal operation

|  | H04M 3/26 |
· · | with means for applying test signals

|  | H04M 3/28 |
· · · | Automatic routine testing

|  | H04M 3/30 |
· · · · | for subscribers' lines

|  | H04M 3/32 |
· · · · | for lines between exchanges

|  | H04M 3/34 |
· · · | Testing for cross-talk (in lines generally Fulltext... Hierarchy... Expanded...H04B)

|  | H04M 3/36 |
· · | Statistical metering, e.g. recording occasions when traffic exceeds capacity of trunks (digital computers for evaluating statistical data Fulltext... Hierarchy... Expanded...G06F 15/36)

|  | H04M 3/38 |
· | Graded-service arrangement, i.e. some subscribers prevented from establishing certain connections (queueing arrangements Fulltext... Hierarchy... Expanded...H04Q 3/64)

|  | H04M 3/40 |
· | Applications of speech amplifiers

|  | H04M 3/42 |
· | Systems providing special services to subscribers

|  | H04M 3/44 |
· · | Additional connecting arrangements for providing access to frequently-wanted subscribers

|  | H04M 3/46 |
· · | Arrangements for calling a number of substations in a predetermined sequence until an answer is obtained

|  | H04M 3/48 |
· · | Arrangements for recalling a calling subscriber when the wanted subscriber ceases to be busy

|  | H04M 3/50 |
· · | Centralised arrangements for answering calls; Centralised arrangements for recording messages for absent subscribers (centralised dictation systems Fulltext... Hierarchy... Expanded...H04M 11/10)

|  | H04M 3/52 |
· · · | Arrangements for routing dead-number calls to operators

|  | H04M 3/54 |
· · | Arrangements for diverting calls for one subscriber to another predetermined subscriber

|  | H04M 3/56 |
· · | Arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities

|  | H04M 3/58 |
· · | Arrangements for transferring received calls from one subscriber to another; Arrangements affording interim conversations between either the calling or the called party and a third party

|  | H04M 3/60 |
· | Semi-automatic systems, i.e. in which the numerical selection of the outgoing line is under the control of an operator

|  | H04M 3/62 |
· · | Keyboard equipment

|  | H04M 3/64 |
· · | Arrangements for signalling the number or class of the calling line to the operator (between operators in inter-exchange working Fulltext... Hierarchy... Expanded...H04M 5/18)

|  | H04M 5/00 |
Manual exchanges (substation equipment in general Fulltext... Hierarchy... Expanded...H04M 1/00)

|  | H04M 5/02 |
· | Constructional details (jacks, jack-plugs Fulltext... Hierarchy... Expanded...H01R 17/00, Fulltext... Hierarchy... Expanded...H01R 21/00)

|  | H04M 5/04 |
· | Arrangements for indicating calls or supervising connections for calling or clearing

|  | H04M 5/06 |
· · | affording automatic call distribution

|  | H04M 5/08 |
· | using connecting means other than cords

|  | H04M 5/10 |
· | using separate plug for each subscriber

|  | H04M 5/12 |
· | Ringing or otherwise calling substations

|  | H04M 5/14 |
· | Applications of speech amplifiers

|  | H04M 5/16 |
· | with means for reducing interference; with means for reducing effects due to line faults

|  | H04M 5/18 |
· | Arrangements for signalling the class or number of called or calling line from one exchange to another

|  | H04M 5/20 |
· · | Number-indicating arrangements for incoming lines

|  | H04M 7/00 |
Interconnection arrangements between switching centres (transmission arrangements in general Fulltext... Hierarchy... Expanded...H04B)

|  | H04M 7/02 |
· | modified to compensate for differences of ground potential

|  | H04M 7/04 |
· | modified to compensate for differences of line impedance

|  | H04M 7/06 |
· | using auxiliary connections for control or supervision

|  | H04M 7/08 |
· | adapted for phantom working

|  | H04M 7/10 |
· | adapted for two-way working, i.e. calls may be set-up in either direction over the same connection

|  | H04M 7/12 |
· | adapted for working between exchanges having different types of switching equipment, e.g. power-driven and step by step, decimal and non-decimal

|  | H04M 7/14 |
· | in systems involving main and subordinate switching centres (current supply source at subordinate switching centre charged from main exchange Fulltext... Hierarchy... Expanded...H04M 19/06)

|  | H04M 7/16 |
· | in systems employing carrier frequencies

|  | H04M 9/00 |
Interconnection arrangements not involving centralised switching

|  | H04M 9/02 |
· | involving a common line for all parties

|  | H04M 9/04 |
· | involving a separate line for each pair of parties

|  | H04M 9/06 |
· | involving combinations of interconnecting lines

|  | H04M 9/08 |
· | Two-way loud-speaking telephone systems with means for suppressing echoes or otherwise conditioning for one or other direction of traffic (for line transmission in general Fulltext... Hierarchy... Expanded...H04B 3/20)

|  | H04M 9/10 |
· · | with switching of direction of transmission by voice frequency

|  | H04M 11/00 |
Telephonic communication systems adapted for combination with other electrical systems

|  | H04M 11/02 |
· | with bell or annunciator systems (such systems in general Fulltext... Hierarchy... Expanded...G08)

|  | H04M 11/04 |
· | with fire, police, burglar, or other alarm systems (such systems in general Fulltext... Hierarchy... Expanded...G08)

|  | H04M 11/06 |
· | Simultaneous speech and telegraphic or other data transmission over the same conductors (transmission of digital information in general Fulltext... Hierarchy... Expanded...H04L)

|  | H04M 11/08 |
· | adapted for optional reception of entertainment or informative matter (systems in which the information is continuously available on a carrier over the whole network Fulltext... Hierarchy... Expanded...H04H 1/08)

|  | H04M 11/10 |
· | with dictation recording and playback systems (such systems in general Fulltext... Hierarchy... Expanded...G11B)

|  | H04M 13/00 |
Party-line systems (substation equipment Fulltext... Hierarchy... Expanded...H04M 1/00; exchange equipment Fulltext... Hierarchy... Expanded...H04M 3/00, Fulltext... Hierarchy... Expanded...H04M 5/00; metering arrangements Fulltext... Hierarchy... Expanded...H04M 15/36)

|  | H04M 15/00 |
Metering arrangements; Time-controlling arrangements; Time-indicating arrangements (counters per se Fulltext... Hierarchy... Expanded...G06M, Fulltext... Hierarchy... Expanded...H03K)

|  | H04M 15/02 |
· | Severing connection after predetermined time

|  | H04M 15/04 |
· | Recording calls in printed, perforated, or other permanent form

|  | H04M 15/06 |
· · | Recording class or number of calling or of called party

|  | H04M 15/08 |
· | Metering calls to called party

|  | H04M 15/10 |
· | Metering calls from calling party

|  | H04M 15/12 |
· · | Discriminative metering

|  | H04M 15/14 |
· · · | according to class of calling party

|  | H04M 15/16 |
· · · | according to connection obtained

|  | H04M 15/18 |
· · · | according to duration of call

|  | H04M 15/20 |
· · · · | Operator's time recording or indicating arrangements

|  | H04M 15/22 |
· · · | according to time of day

|  | H04M 15/24 |
· · · | Preventing metering of tax-free calls to certain lines, e.g. to fire or ambulance stations

|  | H04M 15/26 |
· · | Meter at exchange controlled by operator

|  | H04M 15/28 |
· | with meter at substation

|  | H04M 15/30 |
· · | Meter not controlled from exchange

|  | H04M 15/32 |
· | Metering arrangements for satellites or concentrators which connect one or more exchange lines with a group of local lines

|  | H04M 15/34 |
· | Metering arrangements for private branch exchanges

|  | H04M 15/36 |
· | Metering arrangements for party-lines

|  | H04M 15/38 |
· | Metering by apparatus not of the mechanical step-by-step counter type

|  | H04M 17/00 |
Prepayment telephone systems

|  | H04M 17/02 |
· | Coin-freed or check-freed systems (coin-freed or check-freed apparatus per se Fulltext... Hierarchy... Expanded...G07F)

|  | H04M 19/00 |
Current supply arrangements for telephone systems (for selecting equipment Fulltext... Hierarchy... Expanded...H04Q 1/28)

|  | H04M 19/02 |
· | providing ringing current or supervisory tones, e.g. dialling tone, busy tone

|  | H04M 19/04 |
· · | ringing-current generated at substation

|  | H04M 19/06 |
· | Current supply source at subordinate switching centre charged from main exchange

|  | H04M 19/08 |
· | Current supply source at substation (generating ringing current Fulltext... Hierarchy... Expanded...H04M 19/04)