1、 CEPT T/CD*03-OL*E 80 2326434 O003563 3 -1 69 TCD03-01 Page E 1 Recommendation T/CD 03-01 E (Brussels 1980, revised at Cannes 1983) Concerning the specification of engineering requirements for code dependent time division multiplex equipment for anisochronous telegraph and data transmission Recommen
2、dation prepared by the Working Group T/WG 10 “Data Communications” (CD) Text of the revised Recommendation adopted by the “Telecommunications” Commission, “The Conference of European Post and Telecommunications Administrations, Considering - that CCITT Recommendation R.lO1 describes the standard for
3、 a code and speed dependent TDM system for - that GT/CD has studied the harmonisation of multiplex equipment for data communication under the auspices anisochronous telegraph and data transmission using bit interleaving; of Question CD 1. Recommends - that the attached specification of engineering r
4、equirements for code dependent time division multiplex equipment for anisochronous telegraph and data transmission as annexed to this Recommendation should be taken into account by all CEPT Administrations when implementation of such a piece of equipment is being planned by Administrations.” e Admin
5、istrations are free to stipulate additional requirements, and also which of the optional requirements, if any, are to be provided. Note I: It should be noted that the specification may be revised from time to time. Note 2: The Annex is an integral part of the Recommendation. Edition of March 15, 198
6、6 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. CEPT T/CD*03-OL*E 80 2326414 0003564 5 k T/CD 03-01 E Page 3 Contents SCOPE . GENERAL . COMPONENTS . GENERAL REQUIREMENTS TRIBUTARY CHANNELS FRAME STRUCTURE SYNCHRONISATION TELEX SIGNALLING POWER SUPPLY UNIT . CONTROLS, MONITORS AND ALARMS. MODEMANDAGGREGATEI
7、NTERFACE REFERENCES . 3 3 4 4 5 8 10 13 16 16 18 20 Appendix 1-2 1. 1.1. 1.2. 1.3. 2. 2.1. SCOPE This specification details the facilities and performance required of a code and speed dependent time division multiplex equipment (hereinafter referred to as the equipment) using bit interleaving for an
8、isochronous telegraph and data services. The equipment shall be capable of multiplexing in a pre-determined manner, a maximum of 46, 50 baud channels (or correspondingly fewer channels at rates up to 300 bauds) onto one high bit rate isochronous data stream. It shall also provide an equivalent demul
9、tiplexing facility. The equipment shall be required to interwork with other equipments conforming to CCII“ Recommendation R. 101. The equipment shall be capable of incorporating an internal data modem complying with CCITT Recom- mendation V.26 Alternative B for transmission over a 4 wire speech circ
10、uit at a nominal rate of 2,400 bit/s. It shall also be possible to access the high bit rate data stream for transmission via an external data modem or a higher order of multiplex. GENERAL Design The equipment shall be modular in construction, the modules, each of which may consist of one or more car
11、ds, shall be as shown in Figure 1 (T/CD 03-01). It shall be suitable for the environmental conditions described in CEPT Recommendation T/TR 02-03. Edition of March 15, 1986 CEPT T/CD*03-OL*E 80 I 2326434 0003565 7 * - w Tributary interface I I conversion unit * - T/CD 03-01 E Page 4 Tributary channe
12、l logic External tributary interface Internal tributary interface I 1 As above for other channels I 2.2. I I Tributary part Multiplexing part Multi- plexing logic Internal aggregate inter face I 1 T I Multi- plexed interface con- version unit Aggregate interface pari Figure 1 (T/CD 03-01). Functiona
13、l structure and interfaces of multiplexer. External aggregate inter face I -L I - I Polarity conventions The convention used for polarity shall, for the purposes of this specification, be as follows: SPACE MARK START STOP A Z Binary O Binary 1 Positive Negative ON OFF Note: When applied to the Inter
14、nal aggregate interface the relationship between the positive/negative and ON/OFF conventions are undefined. The External tributary interface shall have a switchable polarity convention. 3, COMPONENTS All components shall comply with the appropriate international specifications. 4. GENERAL REQUIREME
15、NTS 4.1. Multiplexing requirements Tributary channels shall be multiplexed on a bit interleaved basis. The start bit and at least one stop bit of each character shall be transmitted through the aggregate. Edition of March 15, 1986 CEPT T/CD*03-O3*E 2326434 00035bb 9 4.2. 4.3. 4.4. 5. 5.1. 5.2. TJCD0
16、3-01 E Page 5 Alternative structures Two alternative frame structures and associated synchronisation procedures shall be possible in the equipment. These shall be known as Alternative A and Alternative B. Selection between these alternatives may be by any combination of the following means: Replacem
17、ent of one or possibly two common equipment cards. Replacement of modules PROMS, etc., on a common equipment card or cards. Strapping by means of switches, plug in or soldered links, etc. Non volatile programming by means of an external terminal. Equipment practice The equipment practice utilised sh
18、all comply with the appropriate CEPT specification and shall be compat- ible with Type B racks in accordance with CEPT Recommendation T/TR 02-01. Removal and interchangeability of cards Removal and/or replacement of any card unit or module shall not cause any damage to that or any other card unit or
19、 module in the equipment when the equipment is in the “power on” condition. Removal and/or replacement of any card which is peculiar to an individual low rate channel or a restricted number of low rate channels e.g. when one card contains more than one channel, shall not adversely affect the perform
20、ance of channels carried by the remaining cards. The performance of the equipment shall not fall outside the specified limits when similar cards are interchanged among equipments. It shall not be possible to remove a common equipment card without initiating an alarm condition. Cards shall be protect
21、ed from possible damage caused by being inserted into the wrong location, or keyed to prevent incorrect insertion. TRIBUTARY CHANNELS Equipment capacity The equipment shall be designed to multiplex a maximum of 46, 50 baud channels. Channel modulation rates The equipment shall be capable of operatin
22、g at any of the rates and character structures shown in Table 1 (T/CD 03-01), which also includes the maximum capacities for homogeneous channel configurations. Alternative A Alternative B Modulation rate (bauds) 50 75 50 15 1 O0 110 134.5 150 200 300 Character structure Character length (bits) 7.5
23、7.5 1.5 7.5 7.5 or Il 9 IO 7.5 or Stop element (bits) 1.5 1.5 1.5 1.5 1.5 1 1 2 1 I 2 :i 2 Maximum number of homogeneous channels 46 22 46 30 22 22 15 15 10 7 Table 1 (T/CD 03-01). Channel modulation rates and equipment capacity. Edition of March i 5, 1986 CEPT T/CD*03-O3*E 2326434 00035b7 O M TlCD0
24、3-01 E Signal ground or common return Tributary channel transmitted data Tributary channel received data Loop control (optional) Received line signal detector (optional) Page 6 5.2.1. 5.2.2. 5.2.2.1. 5.2.2.2. 5.3. 5.3.1. 5.3.2. 5.4. 5.4.1. 5.4.2, 5.4.3. 5.4.4. 5.4.5. X X X X There shall be no restri
25、ction on the continuous transmission of any combination of data bits within any character at any of the rates (within the limits given in paragraph 5.4.) and character structures detailed in Table 1 (T/CD 03-01). For Alternative B, the equipment shall be capable of multiplexing any combination of up
26、 to eight different rates and character structures detailed in Table 1 (T/CD 03-01) simultaneously. 110 baud characters shall be transmitted on a 100 bit/s bearer channel by transmitting at least one stop bit in the aggregate signal. They shall then be restituted at the correct rate at the channel o
27、utput. 134.5 baud characters shall be transmitted on a 150 bit/s bearer channel by transmitting the necessary additional fill bit of mark polarity before the start element of each character on the aggregate signal. They shall then be restituted at the correct rate at the channel output. Tributary in
28、terfaces External tributary interface Three main variants of the interface exist: i) Low level d.c., (CCITT Recommendation V.28 compatible). ii) High level d.c. iii) Frequency shift voice frequency, e.g. CEPT Recommendation T/CD 01-09. The performance of the multiplexer defined in subsequent paragra
29、phs for the start-stop channel inputs and outputs, shall be measured at the External tributary interface when using a Tributary interface conversion unit in accordance with variant i) above. It shall be possible to use any or all of the variants within the same multiplexer. Internal tributary interf
30、ace The Internal tributary interface is defined by the functional interface circuits as given in Table 2 (T/CD 03-01). Designation G TT TR TLC TA Description I Direction I Table 2 (T/CD 03-01). Internal tributary interface circuits. The electrical characteristics of the interface could be defined by
31、 the logic circuits. The functional interface circuits may or may not be accessible as a physical interface. Tributary channel inputs The equipment shall be capable of transmitting, without error, continuous 50 and 75 bauds, f1.4%, start-stop signals having a stop element length of 1.4 units. For ra
32、tes other than 50 and 75 bauds the equipment shall accept a variation of at least The equipment shall be capable of transmitting, without error, isolated incoming 50 or 75 bauds start-stop signals that have a 1 unit stop element occurring at a maximum rate of 1 per second. The equipment shall be cap
33、able of transmitting, without error, undistorted successive continuous characters at nominal rates of 50 or 75 bauds having intervals between start elements of 1455/6 or 97Y9 ms respectively. The effective net margin on all channel inputs when undistorted signals are received from a transmitter havi
34、ng a nominal character length and modulation rate shall be at least 40%. At the nominal modulation rate, an input character start element shall be rejected if equal to or less than 0.4 units duration and shall be accepted if equal to or greater than 0.6 units duration. Elements corresponding to spac
35、e polarity (or optionally mark polarity in the case of iii) at the distant multiplexer output shall be inserted in the aggregate stream in the case of: i) Unequipped channels. ii) Equipped but disabled or unallocated channels. iii) Open circuit line condition at the tributary channel input. 1.8% in
36、the modulation rate. Edition of March 15, 1986 CEPT T/CD*03-03*E W 2326434 00035bA 2 W 5.5. 5.5.1. 5.5.2. 5.5.3. 5.5.4. 5.5.5. 5.5.5.1. 5.5.5.2. 5.5.6. 5.6. 5.7. 5.7.1. 5.7.2. T/CD 03-01 E Page 7 Tributary channel outputs The maximum degree of gross start-stop distortion shall be 3% for all modulati
37、on rates detailed in Table 1 The maximum difference between the mean modulation rate of the channel output and the nominal modulation rate shall be 0.2%. When characters having a nominal 1.5 unit stop element are presented at any input rate within the range permitted in this specification, the minim
38、um stop element duration released at the output shall be 1.25 units. When characters having a nominal 1 or 2 unit stop element are presented at any input rate within the range permitted in this specification, the minimum stop element duration released at the output shall be 0.8 or 1.8 units respecti
39、vely. During any of the following failure conditions, channel outputs shall be set as specified in paragraphs 5.5.5.1. and 5.5.5.2. within 4 ms of recognition of the failure. i) Carrier fail-signalled as an OFF condition on circuit MA on the Internal aggregate interface (Table 10 / T/CD 03-01), or o
40、n circuit 109 (Received line signal detector), on the External aggregate interface (Table 11 T/CD 03-01). Loss of synchronisation-as defined in paragraphs 7.2.1.2. or 7.3.1.5. for Alternatives A or B respec- tively. (T/CD 03-01). ii) iii) Aggregate fail-paragraph 10.2.8. refers. Leased channels-two
41、options shall be possible on a per channel basis: i) ii) Circuit switched service-two options shall be possible on a per channel basis: i) ii) Set to steady space polarity. Set to steady mark polarity. Set to steady space polarity. The channel shall automatically be looped back towards the local end
42、 for a period of 5+ 1 seconds, after which the outputs shall revert to steady space. Additionally for Alternative B, the trafic path shall be maintained towards the distant equipment during this loop back period. This loop shall be positioned such as to introduce the maximum transfer delay (paragrap
43、h 5.7.) or other measures shall be included which will give a clear indication, e.g. gearbling of the local record at the sending terminal equipment. Selection between the above options shall be by means of a switch, plug in link, soldered link, or via an external terminal. The loss of sync. of an e
44、quipment is indicated to the distant equipment. When that distant equipment has received one Sync. Request signal, in the case of Alternative A (paragraph 7.2.1.3. refers) or one Out of synchronisation pattern in the case of Alternative B (paragraph 7.3.1.4. refers), the tributary channel outputs sh
45、all be controlled in accordance with paragraph 5.5.5. The delay in controlling these outputs shall not exceed 300 ms (excluding the delay due to the bearer and modems) measured from the original declaration of carrier fail or loss of synchronisation. For Alternative B it shall optionally be possible
46、 to programme individual channels such that no action is taken at the outputs in the event of an equipment detecting an Out of synchronisation pattern-hence allowing trafic through normally in that direction. Channel programming Programming of individual channels for code, rate and signalling mode s
47、hall be non volatile and shall be accomplished by means of switches, plug in links, PROMS, or via an external terminal. The method used shall be clear and simple to enable reprogramming of the equipment to be undertaken in the field. The act of reprogramming of any channel or restricted group of cha
48、nnels shall not adversely affect the performance of any other channels in that equipment. Transfer delay The transfer delay shall be measured from the reception of the start element of a character at an input channel of one equipment until the corresponding start element is delivered from the output
49、 channel of the second equipment. The test shall be undertaken with the equipments connected back to back (excluding the modems). The transfer delay for 50 and 75 baud channels shall not exceed 2.5 bits. The transfer delay for all other rates shall not exceed 3.5 bits. Edition of March 15, 1986 CEPT T/CD*03-O1*E 80 H 2326414 0003567 4 W Number (y5” T/CD 03-01 E PaQe 8 condition corresponding to space polarity on the tributary 6. FRAME STRUCTURE 6.1. General Each frame shall consist of 47 bits, the first bit being used for synchronisation whilst the subsequent 46 bits are used for
