1、 TCD01-07E Page 1 Recommendation T/CD O1 -07 E (Ostende 1979, revised at Cannes 1983) concerning the engineering requirements for a parallel data transmission modem using telephone signalling frequencies for use in the general switched telephone network Recommendation proposed by Working Group T/WG
2、10 “Data Communications” (CD) Text of the revised Recomrriendation adopted by the “Teleconimunicatioris” Commission: “The Conference of European Post and Telecommunications Administrations, Considering - that Recommendation T/CD 01-01 contains the text of the Specifications of the general engineerin
3、g requirements - that working groupe CD has studied the harmonization of such modems under the auspices of Question CD 1. for data circuit terminating equipment for analogue and digital networks; Recommends - that the attached Specification of engineering requirements for a parallel data transmissio
4、n modem using tele- phone signalling frequencies for use in the general switched telephone network as contained in Annex I 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.” O Administ
5、rations are free to stipulate additional requirements, and also which of the optional requirements, if any, are to be provided. Note I: The specification is subject of continuing study and possible amendment. Note 2: The Annex is an integral part of the Recommendation. Edition of November 30, 1985 T
6、JCD O1 -07 E Page 3 Annex 1. Contents Section A. Common requirements . 5 2. Data signalling rates. . 5 3. Interface . 5 4. Modulation and coding. 6 5. Scrambling (not provided for) . 6 6.Timing 6 7. Backward channel. 6 8. Line signal characteristics . 6 9. Out-of-band interference 7 1 O. Performance
7、 requirements . 7 11. Testing and measuring requirements . 7 12. Design and construction 7 13. Specific design requirements. 7 14. Power supply. 7 15. Environmental requirements. 7 1. General . 5 . Section B. Network dependent requirements No specific requirements. Parts of this specifications which
8、 are literally copied from CCITT-Recommendations, are marked with a line in the margin of the paper. Sections which need further study, are marked with an asterisk. Edition of November 30, 1985 T/CD O1 -07 E Page 5 Section A. Coitimon reqriirenieiits 1. GENERAL The modems for central receiving stati
9、ons (instations) for parallel data transmission using telephone signalling frequencies for one-way transmission, where keyboard telephone sets are used as simple transmit- ting stations (outstations), are intended for use in the general switched telephone network only. The modems must meet the requi
10、rements given in the Specification of the general engineering requirements and in this specification. They must comply with CCITT Recommendations V.19 and V.24lV.28. The main characteristics of this recommended modems for parallel data transmission using telephone signalling frequencies are as follo
11、ws : (a) simultaneous reception of two frequencies of two separate sub-assemblies of four frequencies: 2( %) code with 16 different character combinations; (b) reception of frequency pair for more than 30 ms, followed by a silent period of not less than 25 ms; (c) reception with speech protection; (
12、d) existence of a backward channel transmitting either simple acknowledgement signals or analog signals (voice-answering). 2. DATA SIGNALLING RATES The data signalling rate of the keyboard telephone is up to 10 characters per second. O 3. INTERFACES 3.1. Interchange circuits The interchange circuits
13、 to be used are given in the list below. List of interchange circuits: 102 104 105 107 Data set ready. lOS/l 108/2 109 125 Calling indicator. 130 Transmit backward tone. 191 110 Data signal quality detector. 13 1 Received character timing. Note I: To make the interface compatible with the relevant s
14、pecifications of Recommendation T/CD 01-08, the combination A, B, may be transmitted on circuit 104 instead of a pause (?1? on all circuits), provided circuit 107 is in the ON position and circuit 105 is in the OFF position. This simulated idle combination is optional. Note 2: These circuits are req
15、uired if the ?telephone channel? facility is provided in the modem. (Speech channel facility.) Note 3: Circuit 108 must be available either as circuit 108/1: Connect data set to he, or as circuit 108/2: Data terminal ready. For automatic calling, this circuit is used exclusively as circuit 108/2. Th
16、e functions of the above interchange circuits are defined in the Specification of the general engineering requirements T/CD 01-01 and comply with CCITT Recommendation V.24. Signal ground or common return. Received data (8 circuits). These circuits are designated Al, A2 . B, according to their corres
17、pon- dence with the relevant frequency in Table 1 (see Note I below). Request to send (see Note 2 below). Connect data set to line (see Note 3 below). Data terminal ready (see Note 3 below). Data channel received line signal detector. Transmitted voice answer (see Note 2 below). 3.2. Interchange cir
18、cuit connector The allocation of the interchange circuits to pins of the connector is in conformance with IS0 Standard 2110. It is given in Annex I. 3.3. Electrical characteristics The electrical characteristics of the above interchange circuits are given in the Specification of the general engineer
19、ing requirements (Recommendation T/CD O 1-01) and comply with CCITT Recommendation V.28. Edition of November 30, 1985 . . T/CD O1 -07 E Page 6 A, = 697 HZ A2 = 770 HZ A, = 852 HZ A, = 941 HZ 3.4. 4. 4.1. 5. 6. 7. 8. 8.1. 8.2. 8.2.1 1 2 3 A 4 5 6 B 7 8 9 C D * O - - CEPT T/CD*OL-O7*E D 2326434 000332
20、7 5 a Electrical characteristics of interchange circuit 191 The impedance and transmitter requirements must comply with the line requirements for the modem, which are given in the Specification of the general engineering requirements (Recommendation T/CD 01-01). MODULATION AND CODING Data channels T
21、wo groups of 4 frequencies are defined as follows: - low group frequencies: 697, 770, 852, 941 Hz; - high group frequencies: 1209, 1336, 1477, 1633 Hz. The frequency pairs are assigned to the different digits as shown in Table 1. I BI = 1209 HZ I B, = 1336 HZ I B, = 1477 HZ I B, = 1633 HZ Section A.
22、 Table 1. SCRAMBLING: not provided for. TIMING By its very principle, the system is asynchronous; however, it may be useful to provide the DTE, on an optimal basis, with a signal wich indicates the sampling times of the data wires. In this case, it is advisable to use circuit 131, wich will switch f
23、rom OFF to ON when the character reaches the interface, and then back to OFF after a time T. This time will be chosen in such a way that the data are stable at the DTE interface. The value T = 15 ms may be recommended by way of example. This clock may optionally be disabled on reception of a silent
24、period. BACKWARD CHANNEL The frequency of the backward channel for simple audible signalling shall be 420 Hz. It shall be possible to modulate this tone at rates of up to 5 bauds (AM). It shall be possible to use this backward channel simultaneously with the data channels. LINE SIGNAL CHARACTERISTIC
25、S The transmit power levels shall be adjustable as indicated in the Specification of the general engineering requirements (Recommendation T/CD O1 -01). Backward channel Provision shall be made for the following facilities: (a) a speech channel non-simultaneous with forward data; (b) a 420 Hz-backwar
26、d channel for audible or/and electrical signalling (see 7.). For the speech channel the signal specifications shall be the same as for the telephone channel indicated in the Specification of the general engineering requirements (Recommendation T/CD O1 -01). Threshold levels Threshold levels of the d
27、ata channel received signal detector When the level of the received signal in group B exceeds 40 dBm, circuit 109 shall be ON. When the level of this received signal is less than -52 dBm, circuit 109 shall be OFF. The detector circuit which causes circuit 109 to turn ON or OFF shall exhibit hystersi
28、s action such that the level at which the OFF to ON transition occurs shall be at least 2 dB greater than for the ON to OFF transition. Group B was chosen for this purpose because it is the most critical from a received level point of view. a Edition of November 30, 1985 8.3. 8.3.1. 8.3.2. 9. 10. 11
29、. 12. 12.1. 13. 14. 15. CEPT T/CD*OL-O7*E 79 m 232b434 0003328 7 TICD O1 -07 E Page 7 Tolerance Data fieqiiencies tolerames The data frequencies tolerances are defined for the keyboard telephone sets. The difference between each frequency and its nominal frequency must not exceed & 1,8 % of the nomi
30、nal frequency. Apart from the tolerance of +1,8% the (instation) modem receiver shall be capable of accepting an additional difference of & 6 Hz caused by the carrier systems. Backward channel fieqiiency tolerances The tolerances on the 420 Hz-backward channel frequency should be +4 Hz. OUT-OF-BAND
31、INTERFERENCE The limits of the line signal spectrum shall conform to the requirements indicated in the Speciication of the general engineering requirements (Recommendation T/CD O 1-01). PERFORMANCE REQUIREMENTS The performance of the equipment will be evaluated by testing in accordance with the Spec
32、ification for the general engineering requirements (Recommendation T/CD 01-01). In addition to those requirements the following requirements regarding error rate limits and parallel distortion limits apply. The character error rate under GSTN test conditions shall be less The parallel distortion, th
33、at means the time difference of the demodulation in the single frequency groups shall be less 2 m/sec. TESTING AND MEASURING REQUIREMENTS To be able to find the source of errors during a transmission procedure (whether it is in the modem or on the line or in the data terminal equipment), the modem s
34、hall offer test possibilities. The modem shall have a unit which-irrespective of whether the data terminal equipment is connected or not+hecks the received data signals. If the received data signa1 is correct, an audible signal is sent to the transmitted station. DESIGN AND CONSTRUCTION The requirem
35、ents are given in the Specification of the general engineering requirements (Recommendation T/CD 01-01). Maintenance requirements The requirements are given in the Specification of the general engineering requirements (Recommendation T/CD 01-01). SPECIFIC DESIGN REQUIREMENTS No specific requirements
36、. POWER SUPPLY Power consumption shall be less than 20 VA. The requirements are given in the Specification of the general engineering requirements (Recommendation T/CD 01-01). ENVIRONMENTAL REQUIREMENTS The requirements are given in the Specification of the general engineering requirements (Recommen
37、dation T/CD 01-01). O Edition of November 30, 1985 CEPT T/CD*OL-O7UE 232b414 0003129 9 Annex I/Section A T/CD o1 -07 E Page 8 Allocation of the interchange circuits to pins of the connector in conformance with IS0 Standard 2110 CCITT 101 102 Ai 104 A2 A3 A4 B1 B2 B3 B4 I 05 107 108/1 108/2 109 110 1
38、25 130 131 191a 191b Interchange circuit Pin Protective ground or earth 1 Signal ground or common return 24 Received data 3 4 5 6 9 10 11 12 Data set ready 23 Connect data set to line Request to send 20 Data terminal ready 22 Data channel received line signal detector Signal quality detector 2 Calling indicator 21 Received character timing 7 8 Transmit backward channel 19 17 18 Transmitted voice answer Edition of November 30. 1985
