|  | 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; coin-freed or check-freed mechanisms Fulltext... Hierarchy... Expanded...G07F)

|  | 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 1/04 |
· · | 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 1/18 |
· · | 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 E 04 H 1/10)

|  | 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 E 04 H 1/10)

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

|  | H04M 1/26 |
· | Devices for signalling identity of wanted subscriber (constructional features Fulltext... Hierarchy... Expanded...H04M 1/23)

|  | H04M 1/28 |
· · | by interrupting current to generate trains of pulses; by periodically opening and closing contacts to generate trains of pulses

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

|  | 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 1/42 |
· · · | Devices whereby a plurality of digits may be stored simultaneously

|  | H04M 1/44 |
· · · · | with provision only for storing one subscriber number at a time by keyboard or dial

|  | H04M 1/45 |
· · · · | with provision for storing more than one subscriber number at a time, e.g. using toothed disc

|  | H04M 1/46 |
· · · · · | using magnetic recording, e.g. on tape

|  | H04M 1/48 |
· · · · · | using punched cards

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

|  | H04M 1/51 |
· · · | Devices whereby a plurality of digits may be stored simultaneously

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

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

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

|  | 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 1/66 |
· | 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 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 (statistical apparatus in general 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 (telegraphy 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

|  | 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)