Section 721-01: Forms of telecommunications using discrete signals | ![](/icons/ecblank.gif) |
| 721-01-01 | | teleprocessing | ![](/icons/ecblank.gif) |
| 721-01-02 | | data | ![](/icons/ecblank.gif) |
| 721-01-03 | | data communication | ![](/icons/ecblank.gif) |
| 721-01-04 | | data transmission | ![](/icons/ecblank.gif) |
| 721-01-05 | | telematics (services) | ![](/icons/ecblank.gif) |
| 721-01-06 | | telegraphy | ![](/icons/ecblank.gif) |
| 721-01-07 | | alphabetic telegraphy | ![](/icons/ecblank.gif) |
| 721-01-08 | | telewriting | ![](/icons/ecblank.gif) |
| 721-01-09 | | facsimile | ![](/icons/ecblank.gif) |
| 721-01-10 | | document facsimile | ![](/icons/ecblank.gif) |
| 721-01-11 | | picture facsimile | ![](/icons/ecblank.gif) |
| 721-01-12 | | phototelecopy | ![](/icons/ecblank.gif) |
| 721-01-13 | | telegraph service | ![](/icons/ecblank.gif) |
| 721-01-14 | | telegram service | ![](/icons/ecblank.gif) |
| 721-01-15 | | telex (service) | ![](/icons/ecblank.gif) |
| 721-01-16 | | supertelex (service) | ![](/icons/ecblank.gif) |
| 721-01-17 | | teletex (service) | ![](/icons/ecblank.gif) |
Section 721-02: Discretely-timed and digital signals, signal elements | ![](/icons/ecblank.gif) |
| 721-02-01 | | discretely-timed signal | ![](/icons/ecblank.gif) |
| 721-02-02 | | digital signal | ![](/icons/ecblank.gif) |
| 721-02-03 | | analogue signal | ![](/icons/ecblank.gif) |
| 721-02-04 | | sampling (of a signal) | ![](/icons/ecblank.gif) |
| 721-02-05 | | quantization | ![](/icons/ecblank.gif) |
| 721-02-06 | | signal element | ![](/icons/ecblank.gif) |
| 721-02-07 | | digit | ![](/icons/ecblank.gif) |
| 721-02-08 | | binary digit | ![](/icons/ecblank.gif) |
| 721-02-09 | | binary figure | ![](/icons/ecblank.gif) |
| 721-02-10 | | n-ary digit | ![](/icons/ecblank.gif) |
| 721-02-11 | | n-bit byte (1) | ![](/icons/ecblank.gif) |
| 721-02-12 | | doublet | ![](/icons/ecblank.gif) |
| 721-02-13 | | triplet | ![](/icons/ecblank.gif) |
| 721-02-14 | | quartet (byte) | ![](/icons/ecblank.gif) |
| 721-02-15 | | quintet (byte) | ![](/icons/ecblank.gif) |
| 721-02-16 | | sextet (byte) | ![](/icons/ecblank.gif) |
| 721-02-17 | | septet (byte) | ![](/icons/ecblank.gif) |
| 721-02-18 | | byte | ![](/icons/ecblank.gif) |
| 721-02-19 | | n-bit byte (2) | ![](/icons/ecblank.gif) |
| 721-02-20 | | code | ![](/icons/ecblank.gif) |
| 721-02-21 | | code conversion | ![](/icons/ecblank.gif) |
| 721-02-22 | | significant condition | ![](/icons/ecblank.gif) |
| 721-02-23 | | number of significant conditions | ![](/icons/ecblank.gif) |
| 721-02-24 | | two conditions | ![](/icons/ecblank.gif) |
| 721-02-25 | | three conditions | ![](/icons/ecblank.gif) |
| 721-02-26 | | four conditions | ![](/icons/ecblank.gif) |
| 721-02-27 | | change-over | ![](/icons/ecblank.gif) |
| 721-02-28 | | transition | ![](/icons/ecblank.gif) |
| 721-02-29 | | significant instant | ![](/icons/ecblank.gif) |
| 721-02-30 | | significant interval | ![](/icons/ecblank.gif) |
| 721-02-31 | | theoretical duration of a significant interval | ![](/icons/ecblank.gif) |
| 721-02-32 | | unit interval | ![](/icons/ecblank.gif) |
| 721-02-33 | | unit element | ![](/icons/ecblank.gif) |
Section 721-03: Transmission using discretely-timed or digital signals | ![](/icons/ecblank.gif) |
| 721-03-01 | | isochronous, adj | ![](/icons/ecblank.gif) |
| 721-03-02 | | anisochronous, adj | ![](/icons/ecblank.gif) |
| 721-03-03 | | start-stop signal | ![](/icons/ecblank.gif) |
| 721-03-04 | | synchronous | ![](/icons/ecblank.gif) |
| 721-03-05 | | synchronous transmission | ![](/icons/ecblank.gif) |
| 721-03-06 | | anisochronous transmission | ![](/icons/ecblank.gif) |
| 721-03-07 | | start-stop transmission | ![](/icons/ecblank.gif) |
| 721-03-08 | | digital transmission (of a discretely-timed signal) | ![](/icons/ecblank.gif) |
| 721-03-09 | | character | ![](/icons/ecblank.gif) |
| 721-03-10 | | character signal | ![](/icons/ecblank.gif) |
| 721-03-11 | | block | ![](/icons/ecblank.gif) |
| 721-03-12 | | start-of-block signal | ![](/icons/ecblank.gif) |
| 721-03-13 | | end-of-block signal | ![](/icons/ecblank.gif) |
| 721-03-14 | | block signal | ![](/icons/ecblank.gif) |
| 721-03-15 | | start signal | ![](/icons/ecblank.gif) |
| 721-03-16 | | start element | ![](/icons/ecblank.gif) |
| 721-03-17 | | stop signal | ![](/icons/ecblank.gif) |
| 721-03-18 | | stop element | ![](/icons/ecblank.gif) |
| 721-03-19 | | A condition | ![](/icons/ecblank.gif) |
| 721-03-20 | | Z condition | ![](/icons/ecblank.gif) |
| 721-03-21 | | equal length code | ![](/icons/ecblank.gif) |
| 721-03-22 | | n-unit code | ![](/icons/ecblank.gif) |
| 721-03-23 | | code word | ![](/icons/ecblank.gif) |
| 721-03-24 | | A element | ![](/icons/ecblank.gif) |
| 721-03-25 | | Z element | ![](/icons/ecblank.gif) |
| 721-03-26 | | modulation rate | ![](/icons/ecblank.gif) |
| 721-03-27 | | baud | ![](/icons/ecblank.gif) |
| 721-03-28 | | speed conversion | ![](/icons/ecblank.gif) |
| 721-03-29 | | actual transfer rate | ![](/icons/ecblank.gif) |
| 721-03-30 | | binary rate | ![](/icons/ecblank.gif) |
| 721-03-31 | | effective transfer rate | ![](/icons/ecblank.gif) |
Section 721-04: Transmission channels and methods | ![](/icons/ecblank.gif) |
| 721-04-01 | | telephone-type channel | ![](/icons/ecblank.gif) |
| 721-04-02 | | telephone-type circuit | ![](/icons/ecblank.gif) |
| 721-04-03 | | wideband channel | ![](/icons/ecblank.gif) |
| 721-04-04 | | multiplex | ![](/icons/ecblank.gif) |
| 721-04-05 | | multiplexing | ![](/icons/ecblank.gif) |
| 721-04-06 | | demultiplexing | ![](/icons/ecblank.gif) |
| 721-04-07 | | multiplexer | ![](/icons/ecblank.gif) |
| 721-04-08 | | demultiplexer | ![](/icons/ecblank.gif) |
| 721-04-09 | | muldex | ![](/icons/ecblank.gif) |
| 721-04-10 | | multiplex signal | ![](/icons/ecblank.gif) |
| 721-04-11 | | time division multiplexing | ![](/icons/ecblank.gif) |
| 721-04-12 | | frequency division multiplexing | ![](/icons/ecblank.gif) |
| 721-04-13 | | homogeneous multiplex | ![](/icons/ecblank.gif) |
| 721-04-14 | | heterogeneous multiplex | ![](/icons/ecblank.gif) |
| 721-04-15 | | simplex, adj and noun | ![](/icons/ecblank.gif) |
| 721-04-16 | | duplex, adj and noun | ![](/icons/ecblank.gif) |
| 721-04-17 | | differential duplex, adj and noun | ![](/icons/ecblank.gif) |
| 721-04-18 | | bridge duplex, adj and noun | ![](/icons/ecblank.gif) |
| 721-04-19 | | incremental duplex | ![](/icons/ecblank.gif) |
| 721-04-20 | | opposition duplex | ![](/icons/ecblank.gif) |
| 721-04-21 | | unidirectional, adj | ![](/icons/ecblank.gif) |
| 721-04-22 | | bidirectional | ![](/icons/ecblank.gif) |
| 721-04-23 | | one-way, adj | ![](/icons/ecblank.gif) |
| 721-04-24 | | both-way, adj | ![](/icons/ecblank.gif) |
| 721-04-25 | | (frequency) channel | ![](/icons/ecblank.gif) |
| 721-04-171 | | differential duplex, adj | ![](/icons/ecblank.gif) |
| 721-04-172 | | differential duplex, noun | ![](/icons/ecblank.gif) |
| 721-04-181 | | bridge duplex, adj | ![](/icons/ecblank.gif) |
| 721-04-182 | | bridge duplex, noun | ![](/icons/ecblank.gif) |
Section 721-05: Direct current transmission | ![](/icons/ecblank.gif) |
| 721-05-01 | | direct current transmission | ![](/icons/ecblank.gif) |
| 721-05-02 | | single current transmission | ![](/icons/ecblank.gif) |
| 721-05-03 | | double current transmission | ![](/icons/ecblank.gif) |
| 721-05-04 | | on-off transmission | ![](/icons/ecblank.gif) |
| 721-05-05 | | sub-telephone transmission | ![](/icons/ecblank.gif) |
| 721-05-06 | | phantom circuit | ![](/icons/ecblank.gif) |
| 721-05-07 | | earth-return phantom circuit | ![](/icons/ecblank.gif) |
| 721-05-08 | | earth-return double phantom circuit | ![](/icons/ecblank.gif) |
| 721-05-09 | | double phantom circuit | ![](/icons/ecblank.gif) |
| 721-05-10 | | Desieter telegraph translation | ![](/icons/ecblank.gif) |
Section 721-06: Carrier transmission, multiplexing | ![](/icons/ecblank.gif) |
| 721-06-01 | | carrier transmission | ![](/icons/ecblank.gif) |
| 721-06-02 | | time division multiplex transmission | ![](/icons/ecblank.gif) |
| 721-06-03 | | differential modulation, <in telegraphy> | ![](/icons/ecblank.gif) |
| 721-06-04 | | modulation with a fixed reference | ![](/icons/ecblank.gif) |
| 721-06-05 | | amplitude shift keying | ![](/icons/ecblank.gif) |
| 721-06-06 | | frequency shift keying | ![](/icons/ecblank.gif) |
| 721-06-07 | | phase shift keying | ![](/icons/ecblank.gif) |
| 721-06-08 | | differential phase shift keying | ![](/icons/ecblank.gif) |
| 721-06-09 | | phase inversion modulation | ![](/icons/ecblank.gif) |
| 721-06-10 | | quadrature phase shift keying | ![](/icons/ecblank.gif) |
| 721-06-11 | | modulation index, <in two-condition frequency shift keying> | ![](/icons/ecblank.gif) |
| 721-06-12 | | coherent modulation | ![](/icons/ecblank.gif) |
| 721-06-13 | | super-telephone transmission | ![](/icons/ecblank.gif) |
| 721-06-14 | | interband transmission | ![](/icons/ecblank.gif) |
| 721-06-15 | | intraband transmission | ![](/icons/ecblank.gif) |
| 721-06-16 | | speech + simplex (equipment) | ![](/icons/ecblank.gif) |
| 721-06-17 | | speech + duplex (equipment) | ![](/icons/ecblank.gif) |
| 721-06-18 | | bisector | ![](/icons/ecblank.gif) |
| 721-06-19 | | first data multiplexer | ![](/icons/ecblank.gif) |
| 721-06-20 | | second data multiplexer | ![](/icons/ecblank.gif) |
| 721-06-21 | | frame, <in time division multiplexing> | ![](/icons/ecblank.gif) |
| 721-06-22 | | sub-frame | ![](/icons/ecblank.gif) |
| 721-06-23 | | frame alignment | ![](/icons/ecblank.gif) |
| 721-06-24 | | frame alignment recovery time | ![](/icons/ecblank.gif) |
Section 721-07: Transmission performance, distortion in time | ![](/icons/ecblank.gif) |
| 721-07-01 | | perfect (discrete) signal | ![](/icons/ecblank.gif) |
| 721-07-02 | | ideal instant | ![](/icons/ecblank.gif) |
| 721-07-03 | | time distortion | ![](/icons/ecblank.gif) |
| 721-07-04 | | incorrect (discrete) signal | ![](/icons/ecblank.gif) |
| 721-07-05 | | degree of individual distortion (of a particular significant instant) | ![](/icons/ecblank.gif) |
| 721-07-06 | | degree of isochronous distortion | ![](/icons/ecblank.gif) |
| 721-07-07 | | degree of start-stop distortion | ![](/icons/ecblank.gif) |
| 721-07-08 | | degree of gross start-stop distortion | ![](/icons/ecblank.gif) |
| 721-07-09 | | degree of synchronous start-stop distortion | ![](/icons/ecblank.gif) |
| 721-07-10 | | degree of standardized test distortion | ![](/icons/ecblank.gif) |
| 721-07-11 | | inherent distortion (of a transmission channel) | ![](/icons/ecblank.gif) |
| 721-07-12 | | bias distortion | ![](/icons/ecblank.gif) |
| 721-07-13 | | degree of bias distortion | ![](/icons/ecblank.gif) |
| 721-07-14 | | characteristic distortion | ![](/icons/ecblank.gif) |
| 721-07-15 | | fortuitous distortion | ![](/icons/ecblank.gif) |
| 721-07-16 | | cyclic distortion | ![](/icons/ecblank.gif) |
| 721-07-17 | | conventional degree of distortion | ![](/icons/ecblank.gif) |
| 721-07-18 | | teledistortion | ![](/icons/ecblank.gif) |
| 721-07-19 | | transmitter distortion | ![](/icons/ecblank.gif) |
| 721-07-20 | | degree of early anisochronous parallel distortion | ![](/icons/ecblank.gif) |
| 721-07-21 | | degree of late anisochronous parallel distortion | ![](/icons/ecblank.gif) |
| 721-07-22 | | margin (of a receiver or other terminal) | ![](/icons/ecblank.gif) |
| 721-07-23 | | net margin | ![](/icons/ecblank.gif) |
| 721-07-24 | | effective margin (of a given apparatus) | ![](/icons/ecblank.gif) |
| 721-07-25 | | nominal margin (of a type of apparatus) | ![](/icons/ecblank.gif) |
| 721-07-26 | | theoretical margin | ![](/icons/ecblank.gif) |
| 721-07-27 | | margin (of a start-stop apparatus) | ![](/icons/ecblank.gif) |
| 721-07-28 | | synchronous (start-stop) margin | ![](/icons/ecblank.gif) |
| 721-07-29 | | margin of a synchronous receiver | ![](/icons/ecblank.gif) |
Section 721-08: Errors and error control | ![](/icons/ecblank.gif) |
| 721-08-01 | | mutilation | ![](/icons/ecblank.gif) |
| 721-08-02 | | erroneous digit | ![](/icons/ecblank.gif) |
| 721-08-03 | | erroneous binary digit | ![](/icons/ecblank.gif) |
| 721-08-04 | | erroneous character | ![](/icons/ecblank.gif) |
| 721-08-05 | | erroneous block | ![](/icons/ecblank.gif) |
| 721-08-06 | | single error | ![](/icons/ecblank.gif) |
| 721-08-07 | | double error | ![](/icons/ecblank.gif) |
| 721-08-08 | | triple error | ![](/icons/ecblank.gif) |
| 721-08-09 | | error burst | ![](/icons/ecblank.gif) |
| 721-08-10 | | error burst length | ![](/icons/ecblank.gif) |
| 721-08-11 | | digit error ratio | ![](/icons/ecblank.gif) |
| 721-08-12 | | character error ratio | ![](/icons/ecblank.gif) |
| 721-08-13 | | block error ratio | ![](/icons/ecblank.gif) |
| 721-08-14 | | error control | ![](/icons/ecblank.gif) |
| 721-08-15 | | block check | ![](/icons/ecblank.gif) |
| 721-08-16 | | error detection | ![](/icons/ecblank.gif) |
| 721-08-17 | | error detection without repetition | ![](/icons/ecblank.gif) |
| 721-08-18 | | loop checking | ![](/icons/ecblank.gif) |
| 721-08-19 | | echoplex | ![](/icons/ecblank.gif) |
| 721-08-20 | | error correction | ![](/icons/ecblank.gif) |
| 721-08-21 | | error detecting and feedback system | ![](/icons/ecblank.gif) |
| 721-08-22 | | error correction by information feedback and repetition | ![](/icons/ecblank.gif) |
| 721-08-23 | | redundant code | ![](/icons/ecblank.gif) |
| 721-08-24 | | code word | ![](/icons/ecblank.gif) |
| 721-08-25 | | Hamming distance | ![](/icons/ecblank.gif) |
| 721-08-26 | | error protection code | ![](/icons/ecblank.gif) |
| 721-08-27 | | error detecting code | ![](/icons/ecblank.gif) |
| 721-08-28 | | error correcting code | ![](/icons/ecblank.gif) |
| 721-08-29 | | constant ratio code | ![](/icons/ecblank.gif) |
| 721-08-30 | | Van Duuren code | ![](/icons/ecblank.gif) |
| 721-08-31 | | cyclic code | ![](/icons/ecblank.gif) |
| 721-08-32 | | contention | ![](/icons/ecblank.gif) |
| 721-08-33 | | recovery procedure | ![](/icons/ecblank.gif) |
| 721-08-34 | | efficiency factor in time (of a transmission with automatic repetition for the correction of errors) | ![](/icons/ecblank.gif) |
| 721-08-35 | | signal repetition | ![](/icons/ecblank.gif) |
| 721-08-36 | | repetition cycle | ![](/icons/ecblank.gif) |
| 721-08-37 | | RQ cycle | ![](/icons/ecblank.gif) |
| 721-08-38 | | BQ cycle | ![](/icons/ecblank.gif) |
| 721-08-39 | | non-print cycle | ![](/icons/ecblank.gif) |
| 721-08-40 | | gated RQ | ![](/icons/ecblank.gif) |
| 721-08-41 | | tested RQ | ![](/icons/ecblank.gif) |
| 721-08-42 | | testing repetition cycle | ![](/icons/ecblank.gif) |
| 721-08-43 | | pre-correction | ![](/icons/ecblank.gif) |
| 721-08-44 | | information bit | ![](/icons/ecblank.gif) |
| 721-08-45 | | service digit | ![](/icons/ecblank.gif) |
| 721-08-46 | | check bit | ![](/icons/ecblank.gif) |
| 721-08-47 | | character check | ![](/icons/ecblank.gif) |
| 721-08-48 | | block check | ![](/icons/ecblank.gif) |
| 721-08-49 | | check digit | ![](/icons/ecblank.gif) |
| 721-08-50 | | even parity check | ![](/icons/ecblank.gif) |
| 721-08-51 | | odd parity check | ![](/icons/ecblank.gif) |
| 721-08-52 | | parity code | ![](/icons/ecblank.gif) |
| 721-08-53 | | parity digit | ![](/icons/ecblank.gif) |
| 721-08-54 | | automatic repetition Verdan system | ![](/icons/ecblank.gif) |
| 721-08-55 | | (signal) quality detection | ![](/icons/ecblank.gif) |
| 721-08-56 | | residual error-rate | ![](/icons/ecblank.gif) |
| 721-08-57 | | information security | ![](/icons/ecblank.gif) |
Section 721-09: Codes and alphabets | ![](/icons/ecblank.gif) |
| 721-09-01 | | message (in telegraphy and data communication) | ![](/icons/ecblank.gif) |
| 721-09-02 | | packet | ![](/icons/ecblank.gif) |
| 721-09-03 | | telegraph signal | ![](/icons/ecblank.gif) |
| 721-09-04 | | data signal | ![](/icons/ecblank.gif) |
| 721-09-05 | | telegraph code | ![](/icons/ecblank.gif) |
| 721-09-06 | | data code | ![](/icons/ecblank.gif) |
| 721-09-07 | | (telegraph) alphabet | ![](/icons/ecblank.gif) |
| 721-09-08 | | n-unit code alphabet | ![](/icons/ecblank.gif) |
| 721-09-09 | | International Telegraph Alphabet No. 1 | ![](/icons/ecblank.gif) |
| 721-09-10 | | International Telegraph Alphabet No. 2 | ![](/icons/ecblank.gif) |
| 721-09-11 | | International Telegraph Alphabet No. 3 | ![](/icons/ecblank.gif) |
| 721-09-12 | | International Telegraph Alphabet No. 4 | ![](/icons/ecblank.gif) |
| 721-09-13 | | International Alphabet No. 5 | ![](/icons/ecblank.gif) |
| 721-09-14 | | telegraph modulation | ![](/icons/ecblank.gif) |
| 721-09-15 | | restitution | ![](/icons/ecblank.gif) |
| 721-09-16 | | isochronous modulation | ![](/icons/ecblank.gif) |
| 721-09-17 | | synchronous telegraphy | ![](/icons/ecblank.gif) |
| 721-09-18 | | synchronous data transmission | ![](/icons/ecblank.gif) |
| 721-09-19 | | start-stop system of telegraphy | ![](/icons/ecblank.gif) |
| 721-09-20 | | start-stop system of data transmission | ![](/icons/ecblank.gif) |
| 721-09-21 | | stepped start-stop system of telegraphy | ![](/icons/ecblank.gif) |
| 721-09-22 | | stepped start-stop system of data transmission | ![](/icons/ecblank.gif) |
| 721-09-23 | | Morse telegraphy | ![](/icons/ecblank.gif) |
| 721-09-24 | | Wheatstone automatic system | ![](/icons/ecblank.gif) |
| 721-09-25 | | Morse code | ![](/icons/ecblank.gif) |
| 721-09-26 | | mark condition (in Morse code) | ![](/icons/ecblank.gif) |
| 721-09-27 | | space condition (in Morse code) | ![](/icons/ecblank.gif) |
| 721-09-28 | | dot (in Morse code) | ![](/icons/ecblank.gif) |
| 721-09-29 | | dash (in Morse code) | ![](/icons/ecblank.gif) |
| 721-09-30 | | space (between characters and words in Morse code) | ![](/icons/ecblank.gif) |
Section 721-10: Function controls and function signals | ![](/icons/ecblank.gif) |
| 721-10-01 | | function control | ![](/icons/ecblank.gif) |
| 721-10-02 | | function signal | ![](/icons/ecblank.gif) |
| 721-10-03 | | control character | ![](/icons/ecblank.gif) |
| 721-10-04 | | translation (in telegraphy and data transmission) | ![](/icons/ecblank.gif) |
| 721-10-05 | | selection (in a telegraph receiver) | ![](/icons/ecblank.gif) |
| 721-10-06 | | local record | ![](/icons/ecblank.gif) |
| 721-10-07 | | format effector | ![](/icons/ecblank.gif) |
| 721-10-08 | | line feed | ![](/icons/ecblank.gif) |
| 721-10-09 | | carriage return | ![](/icons/ecblank.gif) |
| 721-10-10 | | case shift | ![](/icons/ecblank.gif) |
| 721-10-11 | | letters case | ![](/icons/ecblank.gif) |
| 721-10-12 | | letters shift | ![](/icons/ecblank.gif) |
| 721-10-13 | | letter-shift signal | ![](/icons/ecblank.gif) |
| 721-10-14 | | figures case | ![](/icons/ecblank.gif) |
| 721-10-15 | | figures shift | ![](/icons/ecblank.gif) |
| 721-10-16 | | figure-shift signal | ![](/icons/ecblank.gif) |
| 721-10-17 | | space signal | ![](/icons/ecblank.gif) |
| 721-10-18 | | letters shift-on space | ![](/icons/ecblank.gif) |
| 721-10-19 | | erasure signal | ![](/icons/ecblank.gif) |
| 721-10-20 | | "Who are you" signal (function) | ![](/icons/ecblank.gif) |
| 721-10-21 | | answer-back code | ![](/icons/ecblank.gif) |
| 721-10-22 | | synchronisation control | ![](/icons/ecblank.gif) |
| 721-10-23 | | start-of-heading signal | ![](/icons/ecblank.gif) |
| 721-10-24 | | start-of-text signal | ![](/icons/ecblank.gif) |
| 721-10-25 | | end-of-text signal | ![](/icons/ecblank.gif) |
| 721-10-26 | | end-of-transmission signal | ![](/icons/ecblank.gif) |
| 721-10-27 | | transmission control (function) | ![](/icons/ecblank.gif) |
| 721-10-28 | | identification request | ![](/icons/ecblank.gif) |
| 721-10-29 | | acknowledge | ![](/icons/ecblank.gif) |
| 721-10-30 | | negative acknowledge | ![](/icons/ecblank.gif) |
| 721-10-31 | | form feed | ![](/icons/ecblank.gif) |
| 721-10-32 | | horizontal tabulation | ![](/icons/ecblank.gif) |
| 721-10-33 | | vertical tabulation | ![](/icons/ecblank.gif) |
| 721-10-34 | | backspace | ![](/icons/ecblank.gif) |
| 721-10-35 | | device control | ![](/icons/ecblank.gif) |
| 721-10-36 | | cancellation control | ![](/icons/ecblank.gif) |
| 721-10-37 | | substitute character | ![](/icons/ecblank.gif) |
| 721-10-38 | | null character | ![](/icons/ecblank.gif) |
| 721-10-39 | | stuffing character | ![](/icons/ecblank.gif) |
| 721-10-40 | | warning signal | ![](/icons/ecblank.gif) |
| 721-10-41 | | end-of-medium signal | ![](/icons/ecblank.gif) |
| 721-10-42 | | escape | ![](/icons/ecblank.gif) |
| 721-10-43 | | code shift | ![](/icons/ecblank.gif) |
| 721-10-44 | | code reversion | ![](/icons/ecblank.gif) |
| 721-10-45 | | information separator | ![](/icons/ecblank.gif) |
| 721-10-46 | | reversals | ![](/icons/ecblank.gif) |
| 721-10-47 | | switching signal telex-data | ![](/icons/ecblank.gif) |
| 721-10-48 | | call control character | ![](/icons/ecblank.gif) |
| 721-10-49 | | facility request signal | ![](/icons/ecblank.gif) |
| 721-10-50 | | request data transfer | ![](/icons/ecblank.gif) |
Section 721-11: Transmission channels and processes | ![](/icons/ecblank.gif) |
| 721-11-01 | | telegraph channel | ![](/icons/ecblank.gif) |
| 721-11-02 | | data channel | ![](/icons/ecblank.gif) |
| 721-11-03 | | complete telegraph channel | ![](/icons/ecblank.gif) |
| 721-11-04 | | telegraph circuit | ![](/icons/ecblank.gif) |
| 721-11-05 | | data circuit | ![](/icons/ecblank.gif) |
| 721-11-06 | | forward channel | ![](/icons/ecblank.gif) |
| 721-11-07 | | backward channel | ![](/icons/ecblank.gif) |
| 721-11-08 | | status channel | ![](/icons/ecblank.gif) |
| 721-11-09 | | transmit channel | ![](/icons/ecblank.gif) |
| 721-11-10 | | return channel | ![](/icons/ecblank.gif) |
| 721-11-11 | | telegraph repeater | ![](/icons/ecblank.gif) |
| 721-11-12 | | telegraph regenerative repeater | ![](/icons/ecblank.gif) |
| 721-11-13 | | modulation converter | ![](/icons/ecblank.gif) |
| 721-11-14 | | hypothetical reference connection (in telegraphy) | ![](/icons/ecblank.gif) |
| 721-11-15 | | nominated reserved circuit | ![](/icons/ecblank.gif) |
| 721-11-16 | | serial transmission | ![](/icons/ecblank.gif) |
| 721-11-17 | | parallel transmission | ![](/icons/ecblank.gif) |
| 721-11-18 | | coherent significant instants | ![](/icons/ecblank.gif) |
| 721-11-19 | | character-serial transmission | ![](/icons/ecblank.gif) |
| 721-11-20 | | byte-serial transmission | ![](/icons/ecblank.gif) |
| 721-11-21 | | multi-channel | ![](/icons/ecblank.gif) |
| 721-11-22 | | voice-frequency multiplex telegraphy | ![](/icons/ecblank.gif) |
| 721-11-23 | | set of voice-frequency multiplex (telegraph) circuits | ![](/icons/ecblank.gif) |
| 721-11-24 | | burst isochronous | ![](/icons/ecblank.gif) |
| 721-11-25 | | quadruplex system | ![](/icons/ecblank.gif) |
| 721-11-26 | | telegraph multiplex | ![](/icons/ecblank.gif) |
| 721-11-27 | | character interleaved telegraphy | ![](/icons/ecblank.gif) |
| 721-11-28 | | bit-interleaved telegraphy | ![](/icons/ecblank.gif) |
| 721-11-29 | | Baudot telegraphy | ![](/icons/ecblank.gif) |
| 721-11-30 | | Van Duuren radiotelegraph system | ![](/icons/ecblank.gif) |
| 721-11-31 | | frequency shift telegraphy | ![](/icons/ecblank.gif) |
| 721-11-32 | | four-frequency duplex telegraphy | ![](/icons/ecblank.gif) |
| 721-11-33 | | signal recording telegraphy | ![](/icons/ecblank.gif) |
| 721-11-34 | | in-local | ![](/icons/ecblank.gif) |
| 721-11-35 | | automatic retransmission | ![](/icons/ecblank.gif) |
| 721-11-36 | | printing telegraphy | ![](/icons/ecblank.gif) |
| 721-11-37 | | mosaic telegraphy | ![](/icons/ecblank.gif) |
| 721-11-38 | | Hell system | ![](/icons/ecblank.gif) |
| 721-11-39 | | aggregate (isochronous) signal | ![](/icons/ecblank.gif) |
| 721-11-40 | | balanced aggregate signal | ![](/icons/ecblank.gif) |
| 721-11-41 | | multiplex aggregate bit rate | ![](/icons/ecblank.gif) |
| 721-11-42 | | character cycle | ![](/icons/ecblank.gif) |
| 721-11-43 | | element synchronism | ![](/icons/ecblank.gif) |
| 721-11-44 | | element synchronization | ![](/icons/ecblank.gif) |
| 721-11-45 | | synchronization bit | ![](/icons/ecblank.gif) |
| 721-11-46 | | synchronous correction | ![](/icons/ecblank.gif) |
| 721-11-47 | | correction signal | ![](/icons/ecblank.gif) |
| 721-11-48 | | correction from signals | ![](/icons/ecblank.gif) |
| 721-11-49 | | phase relationship, <in synchronous transmission> | ![](/icons/ecblank.gif) |
| 721-11-50 | | character in phase | ![](/icons/ecblank.gif) |
| 721-11-51 | | sub-channel | ![](/icons/ecblank.gif) |
| 721-11-52 | | sub-channel phase transmission | ![](/icons/ecblank.gif) |
| 721-11-53 | | orientation | ![](/icons/ecblank.gif) |
| 721-11-54 | | orientation range | ![](/icons/ecblank.gif) |
| 721-11-55 | | sector | ![](/icons/ecblank.gif) |
| 721-11-56 | | idle circuit condition | ![](/icons/ecblank.gif) |
| 721-11-57 | | inter-character rest condition | ![](/icons/ecblank.gif) |
Section 721-12: Telegraph and data transmission equipments | ![](/icons/ecblank.gif) |
| 721-12-01 | | subscriber's installation | ![](/icons/ecblank.gif) |
| 721-12-02 | | (telegraph) terminal | ![](/icons/ecblank.gif) |
| 721-12-03 | | data terminal equipment | ![](/icons/ecblank.gif) |
| 721-12-04 | | packet mode terminal | ![](/icons/ecblank.gif) |
| 721-12-05 | | data circuit terminating equipment | ![](/icons/ecblank.gif) |
| 721-12-06 | | network termination unit | ![](/icons/ecblank.gif) |
| 721-12-07 | | data station | ![](/icons/ecblank.gif) |
| 721-12-08 | | data source | ![](/icons/ecblank.gif) |
| 721-12-09 | | data sink | ![](/icons/ecblank.gif) |
| 721-12-10 | | modem | ![](/icons/ecblank.gif) |
| 721-12-11 | | interface | ![](/icons/ecblank.gif) |
| 721-12-12 | | interface (specification) | ![](/icons/ecblank.gif) |
| 721-12-13 | | telewriter (1) | ![](/icons/ecblank.gif) |
| 721-12-14 | | start-stop apparatus | ![](/icons/ecblank.gif) |
| 721-12-15 | | teleprinter | ![](/icons/ecblank.gif) |
| 721-12-16 | | page teleprinter | ![](/icons/ecblank.gif) |
| 721-12-17 | | tape teleprinter | ![](/icons/ecblank.gif) |
| 721-12-18 | | alphanumeric keyboard | ![](/icons/ecblank.gif) |
| 721-12-19 | | motorized keyboard | ![](/icons/ecblank.gif) |
| 721-12-20 | | saw-tooth keyboard | ![](/icons/ecblank.gif) |
| 721-12-21 | | storage keyboard | ![](/icons/ecblank.gif) |
| 721-12-22 | | tape-reading head | ![](/icons/ecblank.gif) |
| 721-12-23 | | (teleprinter) control unit | ![](/icons/ecblank.gif) |
| 721-12-24 | | direct printer | ![](/icons/ecblank.gif) |
| 721-12-25 | | (tape) perforator | ![](/icons/ecblank.gif) |
| 721-12-26 | | keyboard perforator | ![](/icons/ecblank.gif) |
| 721-12-27 | | printing perforator | ![](/icons/ecblank.gif) |
| 721-12-28 | | reperforator | ![](/icons/ecblank.gif) |
| 721-12-29 | | printing reperforator | ![](/icons/ecblank.gif) |
| 721-12-30 | | centre holes | ![](/icons/ecblank.gif) |
| 721-12-31 | | chadless perforation | ![](/icons/ecblank.gif) |
| 721-12-32 | | track | ![](/icons/ecblank.gif) |
| 721-12-33 | | telegraph transmitter | ![](/icons/ecblank.gif) |
| 721-12-34 | | keyboard transmitter | ![](/icons/ecblank.gif) |
| 721-12-35 | | automatic transmitter | ![](/icons/ecblank.gif) |
| 721-12-36 | | automatic numbering transmitter | ![](/icons/ecblank.gif) |
| 721-12-37 | | automatic retransmitter | ![](/icons/ecblank.gif) |
| 721-12-38 | | perforated-tape retransmitter | ![](/icons/ecblank.gif) |
| 721-12-39 | | coupled reperforator and tape reader | ![](/icons/ecblank.gif) |
| 721-12-40 | | automatic transmitter with controlled tape-feed mechanism | ![](/icons/ecblank.gif) |
| 721-12-41 | | answer-back unit | ![](/icons/ecblank.gif) |
| 721-12-42 | | answer-back unit simulator | ![](/icons/ecblank.gif) |
| 721-12-43 | | tape printer | ![](/icons/ecblank.gif) |
| 721-12-44 | | Morse key | ![](/icons/ecblank.gif) |
| 721-12-45 | | sounder | ![](/icons/ecblank.gif) |
| 721-12-46 | | Morse undulator | ![](/icons/ecblank.gif) |
| 721-12-47 | | siphon recorder | ![](/icons/ecblank.gif) |
| 721-12-48 | | duplex apparatus | ![](/icons/ecblank.gif) |
| 721-12-49 | | half-duplex apparatus | ![](/icons/ecblank.gif) |
| 721-12-50 | | telegraph relay | ![](/icons/ecblank.gif) |
| 721-12-51 | | vibrating relay (telegraph) | ![](/icons/ecblank.gif) |
| 721-12-52 | | code converter | ![](/icons/ecblank.gif) |
| 721-12-53 | | telegraph modulator | ![](/icons/ecblank.gif) |
| 721-12-54 | | telegraph demodulator | ![](/icons/ecblank.gif) |
| 721-12-55 | | telegraph discriminator | ![](/icons/ecblank.gif) |
| 721-12-56 | | radiotelegraph converter | ![](/icons/ecblank.gif) |
| 721-12-57 | | shift register | ![](/icons/ecblank.gif) |
| 721-12-58 | | acoustic coupling (to a telephone line) | ![](/icons/ecblank.gif) |
| 721-12-59 | | acoustic coupler (for data transmission) | ![](/icons/ecblank.gif) |
Section 721-13: Facsimile equipments and services | ![](/icons/ecblank.gif) |
| 721-13-01 | | document facsimile equipment, Group 1 | ![](/icons/ecblank.gif) |
| 721-13-02 | | document facsimile equipment, Group 2 | ![](/icons/ecblank.gif) |
| 721-13-03 | | document facsimile equipment, Group 3 | ![](/icons/ecblank.gif) |
| 721-13-04 | | drum facsimile transmitter | ![](/icons/ecblank.gif) |
| 721-13-05 | | flat bed facsimile transmitter | ![](/icons/ecblank.gif) |
| 721-13-06 | | drum facsimile receiver | ![](/icons/ecblank.gif) |
| 721-13-07 | | continuous facsimile receiver | ![](/icons/ecblank.gif) |
| 721-13-08 | | telewriter (2) | ![](/icons/ecblank.gif) |
| 721-13-09 | | telefax | ![](/icons/ecblank.gif) |
| 721-13-10 | | datafax | ![](/icons/ecblank.gif) |
| 721-13-11 | | bureaufax | ![](/icons/ecblank.gif) |
Section 721-14: Facsimile operational characteristics | ![](/icons/ecblank.gif) |
| 721-14-01 | | scanning (in facsimile transmitter) | ![](/icons/ecblank.gif) |
| 721-14-02 | | scanning (in facsimile receiver) | ![](/icons/ecblank.gif) |
| 721-14-03 | | scanning spot (at transmission) | ![](/icons/ecblank.gif) |
| 721-14-04 | | scanning spot (at reception) | ![](/icons/ecblank.gif) |
| 721-14-05 | | scanning field | ![](/icons/ecblank.gif) |
| 721-14-06 | | scanning line | ![](/icons/ecblank.gif) |
| 721-14-07 | | scanning line period | ![](/icons/ecblank.gif) |
| 721-14-08 | | scanning line frequency | ![](/icons/ecblank.gif) |
| 721-14-09 | | aspect ratio | ![](/icons/ecblank.gif) |
| 721-14-10 | | picture element | ![](/icons/ecblank.gif) |
| 721-14-11 | | longitudinal resolution (of a facsimile transmitter) | ![](/icons/ecblank.gif) |
| 721-14-12 | | transverse resolution (of a facsimile transmitter) | ![](/icons/ecblank.gif) |
| 721-14-13 | | longitudinal resolution (of a facsimile receiver) | ![](/icons/ecblank.gif) |
| 721-14-14 | | transverse resolution (of a facsimile receiver) | ![](/icons/ecblank.gif) |
| 721-14-15 | | dot frequency | ![](/icons/ecblank.gif) |
| 721-14-16 | | phasing (in facsimile) | ![](/icons/ecblank.gif) |
| 721-14-17 | | phasing signal | ![](/icons/ecblank.gif) |
| 721-14-18 | | phasing on white | ![](/icons/ecblank.gif) |
| 721-14-19 | | phasing on black | ![](/icons/ecblank.gif) |
| 721-14-20 | | synchronization (in facsimile) | ![](/icons/ecblank.gif) |
| 721-14-21 | | aperture (of a facsimile transmitter) | ![](/icons/ecblank.gif) |
| 721-14-22 | | aperture (of a facsimile receiver) | ![](/icons/ecblank.gif) |
| 721-14-23 | | dead sector | ![](/icons/ecblank.gif) |
| 721-14-24 | | lost time | ![](/icons/ecblank.gif) |
| 721-14-25 | | writing helix | ![](/icons/ecblank.gif) |
| 721-14-26 | | writing bar | ![](/icons/ecblank.gif) |
| 721-14-27 | | drum factor | ![](/icons/ecblank.gif) |
| 721-14-28 | | scanning pitch | ![](/icons/ecblank.gif) |
| 721-14-29 | | scanning density | ![](/icons/ecblank.gif) |
| 721-14-30 | | scanning speed | ![](/icons/ecblank.gif) |
| 721-14-31 | | usable scanning line length | ![](/icons/ecblank.gif) |
| 721-14-32 | | total scanning line length | ![](/icons/ecblank.gif) |
| 721-14-33 | | factor of cooperation | ![](/icons/ecblank.gif) |
| 721-14-34 | | index of cooperation | ![](/icons/ecblank.gif) |
| 721-14-35 | | limited scanning | ![](/icons/ecblank.gif) |
| 721-14-36 | | reproduction ratio | ![](/icons/ecblank.gif) |
| 721-14-37 | | positive scanning shift | ![](/icons/ecblank.gif) |
| 721-14-38 | | negative scanning shift | ![](/icons/ecblank.gif) |
| 721-14-39 | | maximum contrast | ![](/icons/ecblank.gif) |
| 721-14-40 | | compression of the luminance range | ![](/icons/ecblank.gif) |
| 721-14-41 | | expansion of the luminance range | ![](/icons/ecblank.gif) |
| 721-14-42 | | luminance compensation | ![](/icons/ecblank.gif) |
| 721-14-43 | | nominal black | ![](/icons/ecblank.gif) |
| 721-14-44 | | nominal white | ![](/icons/ecblank.gif) |
| 721-14-45 | | accentuated contrast | ![](/icons/ecblank.gif) |
| 721-14-46 | | picture black | ![](/icons/ecblank.gif) |
| 721-14-47 | | picture white | ![](/icons/ecblank.gif) |
| 721-14-48 | | tone control aperture | ![](/icons/ecblank.gif) |
| 721-14-49 | | half tone picture | ![](/icons/ecblank.gif) |
| 721-14-50 | | tone wedge | ![](/icons/ecblank.gif) |
Section 721-15: Defects and distortion in facsimile reproduction | ![](/icons/ecblank.gif) |
| 721-15-01 | | aperture distortion | ![](/icons/ecblank.gif) |
| 721-15-02 | | tailing | ![](/icons/ecblank.gif) |
| 721-15-03 | | echo effect | ![](/icons/ecblank.gif) |
| 721-15-04 | | interference pattern (in facsimile) | ![](/icons/ecblank.gif) |
| 721-15-05 | | longitudinal judder | ![](/icons/ecblank.gif) |
| 721-15-06 | | transverse judder | ![](/icons/ecblank.gif) |
| 721-15-07 | | noisy blacks | ![](/icons/ecblank.gif) |
| 721-15-08 | | overlap (in facsimile) | ![](/icons/ecblank.gif) |
| 721-15-09 | | underlap | ![](/icons/ecblank.gif) |
| 721-15-10 | | skew | ![](/icons/ecblank.gif) |
| 721-15-11 | | partial tone reversal | ![](/icons/ecblank.gif) |
Section 721-16: Telegraph and data networks | ![](/icons/ecblank.gif) |
| 721-16-01 | | public telegram network | ![](/icons/ecblank.gif) |
| 721-16-02 | | gentex network | ![](/icons/ecblank.gif) |
| 721-16-03 | | subscriber's line | ![](/icons/ecblank.gif) |
| 721-16-04 | | local line | ![](/icons/ecblank.gif) |
| 721-16-05 | | dedicated circuit (in telegraphy and data transmission) | ![](/icons/ecblank.gif) |
| 721-16-06 | | international circuit | ![](/icons/ecblank.gif) |
| 721-16-07 | | intercontinental circuit | ![](/icons/ecblank.gif) |
| 721-16-08 | | set of circuits | ![](/icons/ecblank.gif) |
| 721-16-09 | | private network (in telegraphy and data transmission) | ![](/icons/ecblank.gif) |
| 721-16-10 | | overflow position | ![](/icons/ecblank.gif) |
| 721-16-11 | | closed private network | ![](/icons/ecblank.gif) |
| 721-16-12 | | interworking between networks | ![](/icons/ecblank.gif) |
| 721-16-13 | | data network | ![](/icons/ecblank.gif) |
| 721-16-14 | | synchronous data network | ![](/icons/ecblank.gif) |
| 721-16-15 | | time base | ![](/icons/ecblank.gif) |
| 721-16-16 | | timescale, <in telecommunication> | ![](/icons/ecblank.gif) |
| 721-16-17 | | cyclic timescale | ![](/icons/ecblank.gif) |
| 721-16-18 | | public data network | ![](/icons/ecblank.gif) |
| 721-16-19 | | node, <in communication networks> | ![](/icons/ecblank.gif) |
| 721-16-20 | | branch (of a data network) | ![](/icons/ecblank.gif) |
| 721-16-21 | | path (of a data network) | ![](/icons/ecblank.gif) |
| 721-16-22 | | (terminal) port (of a network) | ![](/icons/ecblank.gif) |
| 721-16-23 | | data link | ![](/icons/ecblank.gif) |
| 721-16-24 | | circuit switched connection | ![](/icons/ecblank.gif) |
| 721-16-25 | | multipoint connection | ![](/icons/ecblank.gif) |
| 721-16-26 | | point-to-point connection | ![](/icons/ecblank.gif) |
| 721-16-27 | | virtual circuit | ![](/icons/ecblank.gif) |
| 721-16-28 | | permanent virtual circuit | ![](/icons/ecblank.gif) |
| 721-16-29 | | virtual call | ![](/icons/ecblank.gif) |
| 721-16-30 | | transparency (in telegraphy and data transmission) | ![](/icons/ecblank.gif) |
| 721-16-31 | | code independent | ![](/icons/ecblank.gif) |
Section 721-17: Telegraph and data switching, signalling | ![](/icons/ecblank.gif) |
| 721-17-01 | | connection | ![](/icons/ecblank.gif) |
| 721-17-02 | | (complete) connection | ![](/icons/ecblank.gif) |
| 721-17-03 | | (telex) call | ![](/icons/ecblank.gif) |
| 721-17-04 | | subscriber serving exchange | ![](/icons/ecblank.gif) |
| 721-17-05 | | telegraph transit exchange | ![](/icons/ecblank.gif) |
| 721-17-06 | | telegraph switching exchange | ![](/icons/ecblank.gif) |
| 721-17-07 | | data switching exchange | ![](/icons/ecblank.gif) |
| 721-17-08 | | sub-centre | ![](/icons/ecblank.gif) |
| 721-17-09 | | line concentrator | ![](/icons/ecblank.gif) |
| 721-17-10 | | telegraph trunk circuit | ![](/icons/ecblank.gif) |
| 721-17-11 | | telegraph junction circuit | ![](/icons/ecblank.gif) |
| 721-17-12 | | overline service | ![](/icons/ecblank.gif) |
| 721-17-13 | | overflow (in telegraphy) | ![](/icons/ecblank.gif) |
| 721-17-14 | | circuit switching | ![](/icons/ecblank.gif) |
| 721-17-15 | | message switching | ![](/icons/ecblank.gif) |
| 721-17-16 | | packet switching | ![](/icons/ecblank.gif) |
| 721-17-17 | | reperforator switching | ![](/icons/ecblank.gif) |
| 721-17-18 | | character switching | ![](/icons/ecblank.gif) |
| 721-17-19 | | circuit switching exchange | ![](/icons/ecblank.gif) |
| 721-17-20 | | message switching exchange | ![](/icons/ecblank.gif) |
| 721-17-21 | | national subscriber's telex number | ![](/icons/ecblank.gif) |
| 721-17-22 | | local telex number | ![](/icons/ecblank.gif) |
| 721-17-23 | | short code selection | ![](/icons/ecblank.gif) |
| 721-17-24 | | short address | ![](/icons/ecblank.gif) |
| 721-17-25 | | call without selection signals | ![](/icons/ecblank.gif) |
| 721-17-26 | | follow-on-call | ![](/icons/ecblank.gif) |
| 721-17-27 | | selection error correction | ![](/icons/ecblank.gif) |
| 721-17-28 | | alternative selection signals | ![](/icons/ecblank.gif) |
| 721-17-29 | | prefix giving access to the long-distance telex network | ![](/icons/ecblank.gif) |
| 721-17-30 | | prefix giving access to the international telex network | ![](/icons/ecblank.gif) |
| 721-17-31 | | prefix giving access to the intercontinental telex network | ![](/icons/ecblank.gif) |
| 721-17-32 | | destination code | ![](/icons/ecblank.gif) |
| 721-17-33 | | international selection sequence | ![](/icons/ecblank.gif) |
| 721-17-34 | | international two-stage selection | ![](/icons/ecblank.gif) |
| 721-17-35 | | label (in signalling) | ![](/icons/ecblank.gif) |
| 721-17-36 | | traffic routing (in circuit switching) | ![](/icons/ecblank.gif) |
| 721-17-37 | | normal (traffic) routing | ![](/icons/ecblank.gif) |
| 721-17-38 | | alternative traffic routing | ![](/icons/ecblank.gif) |
| 721-17-39 | | first choice set of circuits | ![](/icons/ecblank.gif) |
| 721-17-40 | | emergency routing | ![](/icons/ecblank.gif) |
| 721-17-41 | | re-routing | ![](/icons/ecblank.gif) |
| 721-17-42 | | switching signal | ![](/icons/ecblank.gif) |
| 721-17-43 | | forward switching signal | ![](/icons/ecblank.gif) |
| 721-17-44 | | return switching signal | ![](/icons/ecblank.gif) |
| 721-17-45 | | free circuit condition | ![](/icons/ecblank.gif) |
| 721-17-46 | | ready | ![](/icons/ecblank.gif) |
| 721-17-47 | | not ready | ![](/icons/ecblank.gif) |
| 721-17-48 | | ready for data signal | ![](/icons/ecblank.gif) |
| 721-17-49 | | data channel signalling conditions | ![](/icons/ecblank.gif) |
| 721-17-50 | | calling signal | ![](/icons/ecblank.gif) |
| 721-17-51 | | call control procedure | ![](/icons/ecblank.gif) |
| 721-17-52 | | call-confirmation (signal) | ![](/icons/ecblank.gif) |
| 721-17-53 | | call accepted (signal) | ![](/icons/ecblank.gif) |
| 721-17-54 | | selection signals | ![](/icons/ecblank.gif) |
| 721-17-55 | | address (in circuit switching) | ![](/icons/ecblank.gif) |
| 721-17-56 | | address (in information processing) | ![](/icons/ecblank.gif) |
| 721-17-57 | | proceed-to-select signal | ![](/icons/ecblank.gif) |
| 721-17-58 | | (user) class of service signal | ![](/icons/ecblank.gif) |
| 721-17-59 | | pre-signal | ![](/icons/ecblank.gif) |
| 721-17-60 | | post-signal | ![](/icons/ecblank.gif) |
| 721-17-61 | | end-of-selection signal | ![](/icons/ecblank.gif) |
| 721-17-62 | | keyboard selection | ![](/icons/ecblank.gif) |
| 721-17-63 | | dial selection (in telegraphy switching) | ![](/icons/ecblank.gif) |
| 721-17-64 | | call-connected signal | ![](/icons/ecblank.gif) |
| 721-17-65 | | clearing signal | ![](/icons/ecblank.gif) |
| 721-17-66 | | confirmation of clearing signal | ![](/icons/ecblank.gif) |
| 721-17-67 | | service signal | ![](/icons/ecblank.gif) |
| 721-17-68 | | engaged signal | ![](/icons/ecblank.gif) |
| 721-17-69 | | barred signal | ![](/icons/ecblank.gif) |
| 721-17-70 | | call set-up time | ![](/icons/ecblank.gif) |
| 721-17-71 | | preselection delay | ![](/icons/ecblank.gif) |
| 721-17-72 | | selection time | ![](/icons/ecblank.gif) |
| 721-17-73 | | post-selection time | ![](/icons/ecblank.gif) |
| 721-17-74 | | effective duration of a call | ![](/icons/ecblank.gif) |
| 721-17-75 | | stored program control | ![](/icons/ecblank.gif) |
| 721-17-76 | | common channel signalling | ![](/icons/ecblank.gif) |
| 721-17-77 | | channel associated signalling | ![](/icons/ecblank.gif) |
| 721-17-78 | | call clearing delay | ![](/icons/ecblank.gif) |
| 721-17-79 | | unsuccessful call | ![](/icons/ecblank.gif) |
| 721-17-80 | | call not accepted signal | ![](/icons/ecblank.gif) |
| 721-17-81 | | lost call | ![](/icons/ecblank.gif) |
| 721-17-82 | | head on collision | ![](/icons/ecblank.gif) |
| 721-17-83 | | terminal connection method (in telex) | ![](/icons/ecblank.gif) |
| 721-17-84 | | speed converter concentrator | ![](/icons/ecblank.gif) |
| 721-17-85 | | data concentrator | ![](/icons/ecblank.gif) |
| 721-17-86 | | system control station | ![](/icons/ecblank.gif) |
Section 721-18: Telegraph operation and services | ![](/icons/ecblank.gif) |
| 721-18-01 | | telegram | ![](/icons/ecblank.gif) |
| 721-18-02 | | document facsimile telegram | ![](/icons/ecblank.gif) |
| 721-18-03 | | photograph facsimile telegram | ![](/icons/ecblank.gif) |
| 721-18-04 | | radiotelegram | ![](/icons/ecblank.gif) |
| 721-18-05 | | telex conversation mode | ![](/icons/ecblank.gif) |
| 721-18-06 | | radiotelex call | ![](/icons/ecblank.gif) |
| 721-18-07 | | access to the public telegram network | ![](/icons/ecblank.gif) |
| 721-18-08 | | user class of service | ![](/icons/ecblank.gif) |
| 721-18-09 | | public telex booth | ![](/icons/ecblank.gif) |
| 721-18-10 | | outgoing only terminal | ![](/icons/ecblank.gif) |
| 721-18-11 | | incoming only terminal | ![](/icons/ecblank.gif) |
| 721-18-12 | | access barred | ![](/icons/ecblank.gif) |
| 721-18-13 | | restricted service | ![](/icons/ecblank.gif) |
| 721-18-14 | | priority | ![](/icons/ecblank.gif) |
| 721-18-15 | | absolute priority | ![](/icons/ecblank.gif) |
| 721-18-16 | | priority for called subscriber | ![](/icons/ecblank.gif) |
| 721-18-17 | | in local override | ![](/icons/ecblank.gif) |
| 721-18-18 | | direct outgoing selection | ![](/icons/ecblank.gif) |
| 721-18-19 | | direct incoming selection | ![](/icons/ecblank.gif) |
| 721-18-20 | | direct incoming selection with integrated numbering | ![](/icons/ecblank.gif) |
| 721-18-21 | | direct incoming selection with two-stage selection | ![](/icons/ecblank.gif) |
| 721-18-22 | | closed user group | ![](/icons/ecblank.gif) |
| 721-18-23 | | partially closed user group | ![](/icons/ecblank.gif) |
| 721-18-24 | | interlock code | ![](/icons/ecblank.gif) |
| 721-18-25 | | user facility | ![](/icons/ecblank.gif) |
| 721-18-26 | | automatic calling | ![](/icons/ecblank.gif) |
| 721-18-27 | | automatic answering | ![](/icons/ecblank.gif) |
| 721-18-28 | | manual answering | ![](/icons/ecblank.gif) |
| 721-18-29 | | automatic identification | ![](/icons/ecblank.gif) |
| 721-18-30 | | line identification by the network | ![](/icons/ecblank.gif) |
| 721-18-31 | | automatic date and time indication | ![](/icons/ecblank.gif) |
| 721-18-32 | | indication of duration | ![](/icons/ecblank.gif) |
| 721-18-33 | | indication of charge | ![](/icons/ecblank.gif) |
| 721-18-34 | | statement of call account | ![](/icons/ecblank.gif) |
| 721-18-35 | | shared terminal | ![](/icons/ecblank.gif) |
| 721-18-36 | | accounts for shared terminal | ![](/icons/ecblank.gif) |
| 721-18-37 | | storage of call content | ![](/icons/ecblank.gif) |
| 721-18-38 | | retrieval of stored call content | ![](/icons/ecblank.gif) |
| 721-18-39 | | statistics on request | ![](/icons/ecblank.gif) |
| 721-18-40 | | recorded message | ![](/icons/ecblank.gif) |
| 721-18-41 | | camp-on | ![](/icons/ecblank.gif) |
| 721-18-42 | | camp-on with recall | ![](/icons/ecblank.gif) |
| 721-18-43 | | absent subscriber service (in telegraphy and data communication) | ![](/icons/ecblank.gif) |
| 721-18-44 | | call redirection | ![](/icons/ecblank.gif) |
| 721-18-45 | | changed address interception | ![](/icons/ecblank.gif) |
| 721-18-46 | | store-and-forward | ![](/icons/ecblank.gif) |
| 721-18-47 | | storage installation | ![](/icons/ecblank.gif) |
| 721-18-48 | | redirection address | ![](/icons/ecblank.gif) |
| 721-18-49 | | delayed delivery | ![](/icons/ecblank.gif) |
| 721-18-50 | | message priority | ![](/icons/ecblank.gif) |
| 721-18-51 | | message spacing | ![](/icons/ecblank.gif) |
| 721-18-52 | | header | ![](/icons/ecblank.gif) |
| 721-18-53 | | booked call | ![](/icons/ecblank.gif) |
| 721-18-54 | | network recall | ![](/icons/ecblank.gif) |
| 721-18-55 | | multi-address call | ![](/icons/ecblank.gif) |
| 721-18-56 | | conference call | ![](/icons/ecblank.gif) |
| 721-18-57 | | broadcast call | ![](/icons/ecblank.gif) |
| 721-18-58 | | restricted conference call | ![](/icons/ecblank.gif) |
| 721-18-59 | | broadcast conference call | ![](/icons/ecblank.gif) |
| 721-18-60 | | group call (in a maritime mobile service) | ![](/icons/ecblank.gif) |
| 721-18-61 | | automatic sequential connection | ![](/icons/ecblank.gif) |
| 721-18-62 | | delivery confirmation | ![](/icons/ecblank.gif) |
| 721-18-63 | | telecommunication security | ![](/icons/ecblank.gif) |
| 721-18-64 | | data collection | ![](/icons/ecblank.gif) |
Section 721-19: Data transmission operation and services | ![](/icons/ecblank.gif) |
| 721-19-01 | | link protocol | ![](/icons/ecblank.gif) |
| 721-19-02 | | burst transmission | ![](/icons/ecblank.gif) |
| 721-19-03 | | calling (in data communication) | ![](/icons/ecblank.gif) |
| 721-19-04 | | manual calling (in data communication) | ![](/icons/ecblank.gif) |
| 721-19-05 | | answering (in data communication) | ![](/icons/ecblank.gif) |
| 721-19-06 | | interrogation | ![](/icons/ecblank.gif) |
| 721-19-07 | | polling | ![](/icons/ecblank.gif) |
| 721-19-08 | | selecting, <in telecommunication> | ![](/icons/ecblank.gif) |
| 721-19-09 | | packet sequencing | ![](/icons/ecblank.gif) |
| 721-19-10 | | control station | ![](/icons/ecblank.gif) |
| 721-19-11 | | tributary station | ![](/icons/ecblank.gif) |
| 721-19-12 | | master station | ![](/icons/ecblank.gif) |
| 721-19-13 | | slave station | ![](/icons/ecblank.gif) |
| 721-19-14 | | passive station | ![](/icons/ecblank.gif) |
| 721-19-15 | | primary station | ![](/icons/ecblank.gif) |
| 721-19-16 | | secondary station | ![](/icons/ecblank.gif) |
| 721-19-17 | | combined station | ![](/icons/ecblank.gif) |
| 721-19-18 | | routing (in packet switched data communication) | ![](/icons/ecblank.gif) |
| 721-19-19 | | adaptative routing | ![](/icons/ecblank.gif) |
| 721-19-20 | | packet assembly | ![](/icons/ecblank.gif) |
| 721-19-21 | | packet disassembly | ![](/icons/ecblank.gif) |
| 721-19-22 | | packet format | ![](/icons/ecblank.gif) |
| 721-19-23 | | datagram service | ![](/icons/ecblank.gif) |
| 721-19-24 | | aligner | ![](/icons/ecblank.gif) |
| 721-19-25 | | envelope | ![](/icons/ecblank.gif) |
| 721-19-26 | | permanently locked envelopes | ![](/icons/ecblank.gif) |
| 721-19-27 | | data transfer phase | ![](/icons/ecblank.gif) |
| 721-19-28 | | network control phase | ![](/icons/ecblank.gif) |
| 721-19-29 | | transfer time | ![](/icons/ecblank.gif) |
| 721-19-30 | | flow control | ![](/icons/ecblank.gif) |
| 721-19-31 | | transmit flow control | ![](/icons/ecblank.gif) |
| 721-19-32 | | adaptative channel allocation | ![](/icons/ecblank.gif) |
| ![](/icons/ecblank.gif) |