CEPT T CD 01-02 E-1985 Engineering Requirements for a 300 Bit s Modem for Use on Public Telephone Type Circuits《在公共电话电路上使用的300比特 秒调制解调器工程要求》.pdf

1、I CEPT T/CD*OL-OZ*E 79 H 23264302998 O H I 69 Page E 1 Recommendation T/CD O1 -02 E (Ostende 1979, revised at Cannes 1983) concerning the engineering requirements for a 300 bit/s modem for use on public telephone type circuits Recommendation proposed by Working Group T/WG 10 “Data Communications” (C

2、D) Text of the revised Recommendation adopted by the “Teleconmtrrticntiols” Commission : “The Conference of European Post an Telecommunications Administrations, Considering - that Recommendation T/CD 01-01 contains the text of the Specifications of the general engineering requirements - that Working

3、 Group CD has studied under the auspices of question CD 1 the harmonization of voice band for data circuit terminating equipment for analogue and digital networks; modems for 300 bit/s. Recommends - that the attached Specification of engineering requirements for a 300 bit/s modem for use on the publ

4、ic telephone network as contained in Annex 1 to this Recommendation should be taken into account by all CEPT Administra- tions when implementation of such a piece of equipment is being planned by Administrations.” a Administrations are free to stipulate additional requirements, and also which of the

5、 optional requirements, if any, are to be provided. Note 1: It should be noted that this specification is subjected to continuing study and possible amendments. Note 2: The Annex is an integral part of the Recommendation. a _- y T/CD O1 -02 E Page 3 Annex 1 . Contents Section A . Basic requirements

6、5 1 . General. . 5 2 . Data signalling rates 5 3 . Interface., 5 4 . Modulation and coding . 6 5 . Scrambling 7 6.Timing 7 7 . Backward channel 7 8 . Line signal characteristics 7 9 . Ont of band interference . 7 10 . Performance requirements 7 11 . Testing and measuring requirements 7 12 . Interfac

7、e connector . 7 13 . Specific design requirements . 7 14 . Power supply 7 Section B . National network requirements . 8 15 . Environmental requirements . 7 Section C . Optional requirements . 8 1 . Operation on leased circuits . 8 2 . Receiver sensitivity . 8 3 . Specific design requirements . 8 Edi

8、tion of November 30. 1985 CEPT T/CD*OL-OZ*E 2326414 0003000 3 Interchange circuit Number Designation 102 103 Transmitted data 1 04 Received data Signal ground or common return 106 Ready for sending 107 Data set ready lOS/l 108/2 Data terminal ready 109 Connect data set to line Data channel received

9、line signal detector 125 Calling indicator 140 Loopback/maintenance test 141 Local loopback 142 Test indicator T/CD O1 -02 E Page 5 Public switched telephone network including ter- minals equipped for manual calling, manual an- swering, automatic calling, automatic answering (Note 1) X X X X X X (No

10、te 2) X (Note 2) X X X (Note 3) X (Note 3) X Section A. Basic requirements 1. GENERAL This paper describes the specifications of a full duplex modem to be used on the public telephone network. The modem must meet the requirements given in the Specification of the general engineering requirements (Re

11、commendation T/CD 01-01) and in this specification. It shall also comply with CCITT Recommenda- tion V.24/V.28. 2. DATA SIGNALLING RATES The modem shall use binary frequency modulation and provide facilities for the simultaneous transmission and reception of data at rates up to 300 bit/s over two wi

12、re presented circuits. No coding restrictions shall be imposed on the data signals. However satisfactory operation with modem at a modulation rate of 200 baud according to CCITT Recommendation V.21 should be ensured. 3. INTERFACES 3.1 3.2. Electrical characteristics of interchange circuits The elect

13、rical characteristics of the above mentioned interchange circuits are given in the relevant paragraph of the general engineering requirements (Recommendation T/CD 01-01), complying with CCITT Recom- mendation V.28. 3.3. Automatic answering The modem shall be provided with automatic answering facilit

14、ies according to the relevant part of the general engineering requirements (Recommendation T/CD O1 -0 1). Edition of November 30, 1985 r CEPT T/CD*OL-OZ*E = 2326414 0003001 5 T/CD O1 -02 E Page 6 3.4. 3.5. 3.6. 4. 4.1. 4.2. 4.3. 4.4. 4.5. Response times Definition of response times of interchange ci

15、rcuits 106 und 109: Circuit 109 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 or OFF condition on circuit 109. The test tone should have a frequency corresponding to the char

16、acteristic frequency of binary 1 and be derived from a source with an impedance equal to the nominal input impedance of the modem under test. The level of the test tone should fall into the level range between 1 dB above the actual threshold of the received line signal detector and the maximum admis

17、sible level of the received signal. At all levels within this range the measured response times shall be within the specified limits. Circuit 106 response times are the times from the connection of an ON or OFF condition on: - circuit 105 (where it is provided, see section B) to the appearance of th

18、e corresponding OFF or ON - circuit 109 (where circuit 105 is not provided) to the appearance of the corresponding ON or OFF Response times of circuits 106 and 109 Response times : 106 OFF to ON 20-50 ms (see Note 1) ON to OFF 2 ms. 109 OFF to ON 20 ms (see Note 1) ON to OFF 20-80 ms (see Note I) No

19、te 1: These times are used on leased point-to-point networks without alternate voice-data facilities and on leased multipoint facilities. Note 2: These times are used on PSTN and on leased point-to-point circuits with alternate voice-data. condition on circuit 106; condition on circuit 106. 400-1,00

20、0 ms (see Note 2). 300-700 ms (see Note 2). 20- 80 ms (see Note 2). Receiver sensitivity Threshold greater than -43 dBm circuit 109 ON -48 dBm circuit 109 OFF. The condition of circuit 109 for levels between -43 dBm and -48 dBm is not specified except that the signal detector shall exhibit a hystere

21、sis action such that level at which the OFF to ON transition occurs shall be at least 2 dB greater than for the ON to OFF transition. Clamping to binary 1 condition of circuit 104 Circuit 104 is held in a marking condition (binary 1) under the condition defined below. When this condition does not ex

22、ist the clamp is removed and 104 can respond to the input signals of the modem: - when circuit 109 is in the OFF condition. less than MODULATION AND CODING The modulation is a binary modulation obtained by frequency shift, resulting in a modulation rate being equal to the data signalling rate. For c

23、hannel No. 1, the nominal frequency is 1,080 Hz. For channel No. 2, the nominal frequency is 1,750 Hz. The frequency deviation is I 100 Hz. In each channel, the higher characteristic frequency (FA) corresponds to a binary O. The characteristic frequencies as measured at the modulator output must not

24、 differ by more than f 6 Hz from the national frequencies 1,180/980 Hz and 1,850/1,650 Hz (FA and F, of channels 1 and 2 respectively). Assuming a maximum drift frequency of +6 Hz for the line, the demodulation equipment must tolerate drifts of I12 Hz between the frequencies received and their nomin

25、al values. To ensure interworking of modems of different design and manufacture it is desirable to specify the characteristics of the transmitted line signal. Practical methods are defined in the general engineering requirements (Recommendation T/CD 01-01). e Edition of November 30, 1985 5. SCRAMBLJ

26、NG A scrambler is not provided. 6. TIMING No specific requirement. 7. BACKWARD CHANNEL - CEPT T/CD*OL-OZ*E 79 W 232bYLY 0003002 7 W _ T/CD O1 -02 E Page 7 O O O O Edition of November 30, 1985 7.1. When both channels are used for simultaneous both-way data transmission, channel No. 1 is used for tran

27、smission of the callers data towards the called station, while channel No. 2 is used for transmission in the other direction. 7.2. When one channel is used for data transmission and the other is used for transmission of check signals, service signals, etc., only, it is channel No. 1 which is used fo

28、r transmission from the calling to the called station regardless of the direction in which the data are transmitted. 7.3. For calls set up by operators it is required to override the automatic channel selection e.g. by means of a switch providing normal, called, and answer mode of operation of the m

29、odem. 8. LINE SIGNAL CHARACTERISTICS See general engineering requirements (Recommendation T/CD O 1-01). 9. OUT OF BAND INTERFERENCE See general engineering requirements (Recommendation T/CD O 1-01). 10. PERFORMANCE REQUIREMENTS See engineering requirements (Recommendation T/CD 01-01). 11. TESTING AN

30、D MEASURING REQUIREMENTS 11.1. Test loops: as a minimum requirement test loop 3 as defined in the general engineering requirement (Recommendation T/CD 01-01) shall be provided and controlled both manually by a switch and through the interface (circuit 141). In addition a manually instigated loop sho

31、uld be provided by connection of circuit 103 to 104 (and of circuit 109 to 105 ifprovided) by means of a switch on the modem. 12. INTERFACE CONNECTOR The type of the interface connector and the pin allocation are dened in Recommendation T/CD 01-01, 13. SPECIFIC DESIGN REQUIREMENTS (see also section

32、C) All cords shail come from the back of the modem. AU operation devices (e.g. test loop activation) shall be placed on the front side of the modem. 14. POWER SUPPLY The operating power for the equipment shall be derived from a integrated power unit. For use in a modem rack it might be more economic

33、al to provide the power supply from a rack converter. 15. ENVIRONMENTAL REQUIREMENTS See general engineering requirements (Recommendation T/CD 01-01). CEPT T/CD*OL-OZ*E m 232b414 0003003 9 Number I Designation T/CD 01-02 E Page 8 Point-to-point Multipoint Section B. National network dependent requir

34、ements No further requirements other as those formulated in section B of Recommendation T/CD 01-01 have to be applied. I 126 Section C. Optional requirements I Select transmit frequency I - 1 X (Note4) 1. OPERATION ON LEASED CIRCUITS The list of interchange circuits for application on non-switched l

35、eased telephone circuits for point-to-point or multipoint application is given in Table 2/CD 01-02. Non-switched leased telephone circuits (Note 1) Interchange circuit 102 103 104 105 106 Signal ground or common return X X Transmitted data Received data Request to send Ready for sending X X (Note 2)

36、 X X X X 107 108/2 109 lOS/l Data set ready Connect data set to line Data terminal ready Data channel received line signal detector X X (Note 3) X X X X X - I :“ 142 Loopback/maintenance test Local loopback Test indicator X (Note 5) X (Note 5) X (Note 5) X (Note 5) Table 2 (T/CD 01-02). Note I : Int

37、erchange circuits indicated by X must be properly terminated according to the general specifications (Recommendation T/CD 01-01) relating to the electrical Characteristics in the data terminal equipment and data circuit-terminating equipment. Note 2: Circuit 105 is not required when alternate voice/

38、data service is used on non-switched leased point-to-point circuits. Note 3; In the leased point-to-point case, where alternate voice/data service is to be provided, circuit 108/2 may be used optionally. Note 4: Circuit 126 controls both the transmitter and receiver frequency allocation. Note 5: Loo

39、pback and maintenance test procedure are matter for urgent study. 2. RECEIVER SENSITIVITY For application on leased circuits following threshold should apply: Threshold greater than -33 dBm circuit 109 ON. -38 dBm circuit 109 OFF. The condition of circuit 109 for levels between - 33 dBm and - 38 dBm

40、 is not specified except that the signal detector shall exhibit a hysteresis action such that level at which the OFF to ON transition occurs shall be at least 2 dB greater than for the ON to OFF transition. less than 3. SPECIFIC DESIGN REQUIREMENTS The modem shall allow to be sealed. O Edition of November 30, 1985