1、(3 Page 1 E Recommendation T/CD O1 -03 E (Ostende 1979, revised at Cannes 1983) Concerning the engineering requirements for a 600/1,200 bit/s modem for use on telephone type circuits Recommendation proposed by Working Group T/WG 10 “Data Communications” (CD) Text of the revised Recommendation adopte
2、d by the “Telecoiimimications” Commission : “The Conference of European Post and Telecommunications Administrations, Consider iiig - that Recommendation T/CD 01-01 contains the text of the Specifications of the general engineering requirements - that Working Group CD has studied under the auspices o
3、f question CD 1 the harmonization of voiceband for data circuit termination equipment for use on voiceband, baseband and groupband circuits; modems. Recommenh - that the attached Specification of engineering requirements for a 600/1,200 bit/s modem for use on telephone-type circuits as contained in
4、the Annex 1 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.” Administrations are free to stipulate additional requirements; and also which of the additional requirements, if any, are
5、 to be provided. Note 1: It should be noted that this specification may be revised from time to time. Note 2: The Annex is an integral part of the Recommendation. Note 3: Bars at the left-hand margin indicate that the wording of this specification is identical with CCITT Recommendation V.23 for the
6、relevant item. Edition of November 30, 1985 T/CD o1 -03 E Page 3 Annex 1 . Contents Section A Common requirements . 5 1 . General. . 5 2 . Data signalling rates 5 3 . Interfaces . 5 4 . Modulation . 7 5 . Scrambler . 7 6 . Backwardchannel . 7 7 . Linesignallevel 7 8 . Out-of-band interference . 7 9
7、. Performance requirements 8 10 . Construction 8 11 . Power supply Section B . Network dependent requirements 8 No specsc requirements . Section C . Optional requirements 9 1 . Operation on 2-Mre circuits in the public switched telephone network 9 2 . Operation on leased 2-wire circuits 9 3 . Operat
8、ion on leased 4-wire circuits . 9 4 . Inclusion of a clock in the modem . 9 5 . Automatic answering 9 6 . Backward channel 9 7 . Transmission quality test device 10 8 . Forward (data) channel one-way system 11 Appendix . Table of additional interchange circuits . 12 Edition of November 30. 1985 T/CD
9、 O1 -03 E Page 5 Designation Signal ground or common return Transmitted data Section A. Cottittion reqrirettieiits a (Note i) Without backward channel X X 1. GENERAL This modem is intended for use on connections set up by switching in the public telephone network and on leased lines. This modem shal
10、l meet the requirements given in the Specification for general engineering requirements (Recommendation T/CD 01-01) and in this specification. It shall also comply with the CCITT Recommen- dations V.23 and V.24/V.28. The principal characteristics of this modem are as follows: - use of modulation rat
11、es up to 600/1,200 bauds; - frequency modulation with synchronous or asynchronous mode of operation, the synchronous mode - inclusion of an optional backward channel at modulation rates up to 75 bauds. being optional; 2. DATA SIGNALLING RATES Asynchronous mode: up to 60CJ/lY200 bit/s. 3. INTERFACES
12、3.1, Interchange circuits The interchange circuits essential for the modem are shown in the tab1 No. 102 103 104 105 106 107 108/1 or 108/2 (Note 2) 1 o9 111 140 (Note 3) 141 (Note 3) 142 below. Interchange circuit Forward (data) channel either way or both ways simultaneously system Received data Re
13、quest to send Ready for sending X X X Data set ready Connect data set to line Data terminal ready Data channel received line detector Data signalling rate selector (DTE) Loopback/Maintenance test Local loopback Test indicator X X X X X X X Note 1: Interchange circuits indicated by X must be properly
14、 terminated in the data terminal equipment and data circuit-terminating equipment in accordance with the appropriate Recommendation for electrical characteristics (see paragraph 3.3.). Note 2: This circuit shall be capable of operation as circuit 108/1: “Connect data set to line” or circuit 108/2: “
15、Data terminal ready” depending on its use. For automatic calling it shall be used as 10812 only. Note 3: Loopback procedures is a matter for urgent study. Edition of November 30, 1985 CEP“ T/CD*O1-03*E m 2326414 00030L 9 m Circuit 106 OFF to ON T/CD 01 -03 E Page 6 3.2. Definitions of interchange ci
16、rcuits All interchange circuits and any others wich are provided shall comply with the functional and operational requirements of CCITT Recommendation V.24. 3.3. Electrical Characteristics of interchange circuits The electrical characteristics of the interchange circuits shall conform to CCITT Recom
17、mendation V.28. 3.4. Interchange circuits connector The interchange circuits connector and the pin allocation shall comply with the IS0 standard DIS 21 10. I 3.5. Response times of circuits 106 and 109 DeJinitions i) Circuit 109 response times are the times that elapse between the connection or remo
18、val of a tone to or from the modem receive line terminals and the appearance of the corresponding ON or OFF condition on circuit 109. The test tone should have a frequency corresponding to the characteristic frequency of binary 1 and be derived from a source with an impedance equal to the nominal in
19、put impedance of the modem. The level of the test tone should fall within the level range between 3 dB above the actual threshold of the received line signal detector and the maximum admissible level of the received signal. At all levels within this range the measured response times shall be within
20、the specified limits. ii) Circuit 106 response times are from the connection of an ON or OFF condition on: - circuit 105 (where it is provided) to the appearance of the corresponding ON or OFF condition on - circuit 107 (where circuits 105 and 122 are not provided) to the appearance of the correspon
21、ding ON circuit 106; or OFF condition on circuit 106. Response times ON to OFF Circuit 109 OFF to ON ON to OFF 750 ms to 1,400 ms (see Note I) 2 ms 20 rns to 40 ms (see Note 2) 200 ms to 275 ms (see Note 2) 300 ms to 700 ms (see Note I) 5 ms to 15 ms 10 rns to 20 ms (see Note I) Note I: For automati
22、c calling and answering, the longer response times of circuits 106 and 109 are to be used during call establishment only. Note 2: Strappable. Note 3: The above parameters are provisional and are the subject of further study. Threshold of data channel receive line signal detector Level of received li
23、ne signal at receive line terminals of modem for all types of connections, i.e. general switched telephone network or non-switched leased telephone circuits: greater than -43 dBm circuit 109 ON less than -48 dBm circuit 109 OFF The condition of circuit 109 for levels between -43 dBm and -48 dBm is n
24、ot specified except that the signal detector shall exhibit a hysteresis action such that the level at which the OFF to ON transition occurs is at least 2 dB greater than that for the ON to OFF transition. It shall be possible at the time of modem installation to change these response levels of the r
25、eceived line signal detector to -33 dBm and -38 dBm respectively. 3.6. Edition of November 30, 1985 CEPT T/CD*O3-03*E 77 2326434 000303 O M Mode 1: up to 600 bit/s 1,500 Hz 1,300 Hz Mode 2: up to 1,200 bit/s 1,300 Hz I 1,700 Hz I 3.7. 3.8. 1,700 Hz 2,100 Hz 4. 4.1. 4.2. 5. 6. 7. 8. T/CD O1 -03 E Pag
26、e 7 Clamping in haif-duplex mode The DCE, when operating in half-duplex mode on a two-wire line, shall hold, where implemented, circuit 104 in th: binary 1 condition and circuit 109 in the OFF condition when circuit 105 is in the ON condition and, where required to protect circuit 104 from false sig
27、nals, for a period of 150 + 25 ms following the ON to OFF transition on circuit 105. The use of this additional delay is optional, based on system considerations. Fault condition of interchange circuits See section 7 of CCITT Recommendation V.28 for association of the receiver failure types. i) The
28、DTE should interprete a fault condition on circuit 107 as an OFF condition using failure detection type 1. U) The DCE should interprete a fault condition on circuits 105 and 108 as an OFF condition using failure detection type 1. Ui) All other circuits not referred to above may use failure detection
29、 types O or 1. MODULATION Modulation rates and characteristic frequencies for the forward data-transmission channel It is understood that the modem would be used in mode 1 when the presence of long loaded cables and/or the presence on some connection of signalling receivers operating close to 2,000
30、Hz would prevent satisfac- tory transmission in mode 2. Tolerances on the characteristic frequencies for the forward channel It should be possible whith all rates of modulation to permit a tolerance, at the transmiter, of + 10 Hz on both the FA and Fz frequencies. This tolerance should be considered
31、 as a limit. Acceptance of these tolerances would give a tolerance of + 10 Hz for the mean-frequency Fo = (FA+ F2/2. The tolerance on the frequency difference FA-Fz with regard to the nominal value would be 120 Hz. A maximum frequency drift of +6 Hz has been assumed in the connection between the mod
32、ems which might consist of several carrier circuits connected in tandem. This would make the tolerances on the mark and space frequencies at the receiving modem + 16 Hz. SCRAMBLER Scrambling is not foreseen. BACKWARD CHANNEL The inclusion of a backward channel at modulation rates up to 75 bauds shal
33、l be prepared for but the use of this channel is being optional. The channel is specified in Section C. LINE SIGNAL LEVELS The power transmitted in the forward channel shall be in accordance with the Specification for the general engineering requirements (Recommendation T/CD 01-01). The signal build
34、-up time to 90% of final level shall be 1 ms. The signal decay time to -60 dBm shall be 1 ms. OUT-OF-BAND INTERFERENCE The line signal spectrum shall conform to the Specification for the general engineering requirements (Recommendation T/CD 01-01). Edition of November 30, 1985 - CEPT T/CD*O3-03*E W
35、2326434 00030L 2 TICD O1 -03 E Page 8 9. PERFORMANCE REQUIREMENTS See the Specification for the general engineering requirements (Recommendation T/CD 01-01). 10. CONSTRUCTION The construction of the modem shall comply with the Specification for the general engineering requirements (Recommendation T/
36、CD 01-01). 11. POWER SUPPLY The operation power for the equipment shall be derived from an integral power unit. For use in a modem rack it might be more economical to provide the power supply from a rack converter. a Edition of November 30, 1985 CEPT T/CD*OL-O3*E 77 2326434 0003020 9 _ - T/CD 01-03
37、E Page 9 Section B. Network depetidetif requirettietits No specific requirements. Section C. Optiotial reqrrirettietits 1. OPERATION ON 2-WIRE CIRCUITS IN THE PUBLIC SWITCHED TELEPHONE NETWORK It shall be possible to operate the modem on 2-wire circuits in the public switched telephone network. 2. O
38、PERATION ON LEASED 2-WIRE CIRCWIS It shall be possible to operate the modem on leased 2-wire circuits. 3. OPERATION ON LEASED $-WIRE CIRCUITS It shall be possible to operate the modem on leased 4-wire circuits. 4. 5. 6. 6.1. 6.2. INCLUSION OF A CLOCK IN THE MODEM It shall be possible to include a cl
39、ock in the modem for synchronous mode of operation. When this clock is used in the modem, a synchronizing pattern consisting of alternate binary O and binary 1 at clock rate shall be transmitted for the whole interval between the OFF to ON transitions of interchange circuits 105 and 106. Users shoul
40、d note that part of this synchronizing pattern may appear at the distant receiver on circuit 104 after the OFF to ON transition of circuit 109. The data terminal equipment shall make provision to differential between these false signals and true data. The data signalling rates in the synchronous mod
41、e of operation shall be 600/1,200 bit/s f0.01%. The additional interchange circuits required when this option is called for are listed in the Appendix. AUTOMATIC ANSWERING It shall be possible to provide the modem with automatic answering facilities according to the Specification for the general eng
42、ineering requirements (Recommendation T/CD 01-01). The additional interchange circuit required when this option is called for is listed in the Appendix. BACKWARD CHANNEL It shall be possible to provide the modem with a backward channel according to the following specification. The additional interch
43、ange circuits required when this option is called for are listed in the Appendix. Modulation rate and characteristic frequencies for the backward channel The modulation rate and characteristic frequencies for the backward channel shall be as follows : Fz. FA (symbol 1, mark) (symbol O, space) Modula
44、tion rate up to 75 bauds 390 Hz 450 Hz In the absence of any signal on the backward channel interface, the condition Z signal is to be transmitted. Tolerance on the characteristic frequencies of the backward channel As the backward channel is a VF telegraph-type channel, the frequency tolerance shal
45、l be as follows: - the mean frequency defined as half sum of the two characteristic frequencies, F, and FA, shall not deviate - the difference between the two characteristic frequencies shall not deviate more than 60k3 Hz at the The sending end. Edition of November 30, 1985 7 CEPT T/CD*OL-O3*E M 232
46、b414 0003021 O M T/CD O1 -03 E Page 10 6.3. 6.4. 6.5. 6.6. 7. Response times of circuits 121 and 122 Definitions i) Circuit 122 response times are the times that elapse between the connection or removal of a tone to or from the modem receive line terminals and the appearance of the corresponding ON
47、or OFF condition on circuit 122. The test tone should have a frequency corresponding to the characteristic frequency of binary 1 and be derived from a source with an impedance equal to the nominal input impedance of the modem. The level of the test tone should fall within the level range between 3 d
48、B above the actual threshold of the received line signal detector and the maximum admissible level of the received signal. At all levels within this range the measured response times shall be within the specified limits. ii) Circuit 121 response times are from the connection of an ON or OFF conditio
49、n on: - circuit 120 (where it is provided) to the appearance of the corresponding ON or OFF condition on - circuit 109 (where circuit 120 is not provided) to the appearance of the corresponding ON or OFF circuit 12 1 ; condition on circuit 121. Response times Circuit 121 OFF to ON ON to OFF 80 ms to 160 ms 2ms Circuit 122 OFF to ON ON to OFF 80ms 15 ms to 80 ms Note: The above parameters are provisional and are the subject of further study. Threshold of backward channel received line signal detector Level of received line signal at receive line terminals of modem for all
