1、EIA 210 58 = 3234b00 0063234 T H O Cu rn m w Terminating and Signaling Equipment 4 u for Microwave Communication Systems Part I: Telephone Equipment RS=ZIO August 1958 Engineering Department ELECTRON IC IN DUSTRI ES ASSOCIATION (Fcrrmerly RADIO-ELECTONICS-ION MA“ACWRES ASSOCUTION) Copyright Telecomm
2、unications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-EIA 210 58 = 3234600 0063235 1 NOTICE EIA standards are adopted in the public interest and are designed to eliminate misunder- standings between th
3、e manufacturer and the purchaser and to assist the purchaser in selecting tirici obtaining without delay tlie proper product for its particular need. Existence of such stand- ards does not in any respect preclude any member or non-member of EIA from manufacturing or selling products not conforming t
4、o the standard. Any proposal of recommended standards and practices made by the Association is without any regard to whether or not their adoption may in any way involve patents on articles, materiais or . processes,-,By such action, the Association does not assume any liability to any patent owner,
5、 nor does it assume any obligation whatever ,to parties adopting the recommended standards or practices. Published by ELECTRONIC INDUSTRI ES ASSOCIATION Engineering Department 2001 Eye Street, N.W., Washington, D. C. 20006 Copyright 1968 by Electronic Indiutrfem AssocMion Ali rfphta renerved Copyrig
6、ht Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-EIA 210 58 W 3234600 0063236 3 - RS-2 1 O Page 1 Terminating and Signaling Equipment for Microwave Communication Systems Part I: Telepho
7、ne Equipment (From Standards Proposal Nos. 518 and 553, formlatsd under the cognizance of EIA Engineerixg Committee TR-14 on Microwave Relay Systems for Communications) TABLE OF CONTENTS 1. INTRODUCTION 2. STANDARDS FOR TALKING CIRCUITS 2.1 Net System Loop Gain 2.2 Return Loss 2.3 Net Loss 2.4 Singi
8、ng Margin 2.5 Talker Echo 2.6 Insertion Loss 2.7 Characteristics of Connected Equipment 2.8 Longitudinal Balance 2.9 Battery Voltage 3. STANDARDS FOR SIGNALING CIRCUITS 3.1 Loop Resistance 3.2 Loop Leakage Resistance 3.3 Ringing Current 3.4 Ringing Voltage 3.5 Impedance of Devices Responding to Ring
9、ing 3.6 Battery Voltage 3.7 Pulse Signaling 3.8 Dial Pulsing Speed 3.9 Per Cent Break 3.10 Signaling Pulse Distortion 4. SUPPLEMENTARY DEFINITIONS 4.1 Definitions from Other Sources Copyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction
10、or networking permitted without license from IHS-,-,-EIA 210 58 3234b00 00b3237 5 i RS-2 1 O Page 2 1. INTRODUCTION The standards included in Part 1 are for Terminating and Signaling equipment to be used in Tele- phone Service. Subsequent parts will cover such services as Data Transmission, Remote C
11、ontrol, Teletype, Facsimile, and so on. Because there are so many accepted practices in the telephone industry, each devised to meet per- tinent requirements in specific situations, it is difficult to reduce these practices to a single standard for Terminating and Signaling equipment for Telephone S
12、ervice. Where it appears impractical to establish a numerical value for a Standard, examples of current practices, or informative notes on relative importance, have been given. One of the most important considerations is the achievement of a common acceptance of terms and . their definitions. Wherev
13、er possible, terminology already established by recognized organizations have been used. Where no previously accepted terms and definitions were available, they were pre- pared by the cognizant EIA Engineering Committee. A list of applicable terms, their sponsors and reference, is included in this S
14、tandard. a 2. STANDARDS FOR TALKING CIRCUITS Note: In view of the many permutations and combinations of available terminating arrangements and terminating requirements, it is necessary to analyze each applicatbn individuully in order to ascertain the exact equipment arrangements which must be suppli
15、ed as part of the Terminating Equipment. 2.1 Net System Loop Gain 2.1.1 Definition: Net System Loop Gain is the algebraic sum of all the gains and losses included in a possible singing path associateu with a system. 2.1.2 Standard: Not applicable. 2.1.3 Method of Measurement: To measure the net syst
16、em loop gain of the channel (see Figure 1) the transmit branch of the hybrid set at one end shall be disconnected from the telephone channel and properly terminated. A test signal, at a power level corresponding to that of the Telephone Channel Test Signal at this point in the system, shall be appli
17、ed to the transmit side of the channel, and the power output measured at the transmit side of the hybrid. The net system loop gain is the ratio of the power received to the power of the test signal, and is usually expressed in db. TR REC 7- I MICROWAVE + MULTIPLEX -=- TERMINATION EQUIPMENT a-+ ./ RE
18、C Fig. 1 2.2 Reium LOEE 2.2.1 Definition: (Amended from ASA 66:08:123). The return loss at the junction of a trans- mission line and a terminating impedance is the ratio, expredsed in db, of the incident wave to the reflected wave. More broadly, the return loss is a measure of the dissimilarity betw
19、een two impedances, being equal to the scalar value of the reciprocal of the reflection coefficient, and hence being expressed by the formula: - y- -_ Copyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without
20、 license from IHS-,-,-EIA 210 58 3234600 O063238 7 W 201og10 I g: :E: 1 db where Z1 and Z2 are the two impedances. 2.2.2 Standard: The minimum value of return loss of hybrid sets is primarily determined by the range of load impedances (see 2.7) presented to the 2-wire branch of the hybrid sets by th
21、e con- nected equipment (such as telephone sets, cable circuits, Central Office equipment, etc.). It is therefore impractical to set a numerical value as a Standard for return loss. Noter The minimum return loss encountered under busy conditions Will determine, to a large extent, the minimum net los
22、s at which the circuit can be operated and still meet the requirements for Singing Margin and Echo Margh 2.2.3 Method of Measurement: The Transmit Branch of the Hybrid Set shall be disconnected from the Telephone Channel and properly terminated. A test signal at a power level corresponding to that o
23、f the Telephone Channel Test Signal at this point in the system shall be applied to the Receive Branch of the Hybrid set, and the power of the reflected signal measured at the Transmit Branch. (See Figure 2). The Return Loss in db is then given by : Return loss (db) = Ratio of test signal power to r
24、eflected signal power (db) - the sum of the insertion losses of the Transmit and Receive Branches of the Hybrid Set. Note: Tht measurement shall be made with the two-wire branch of the Hybrid Set so terminated as to present the minimum Return Loss normally encountered in service, and at that frequen
25、cy at which the Return Loss has its lowest value. It will usually be necessary to resort to trial and error in order to achieve this condition. TERMINATIONI-HYBRID 1-1 BAL. I (SEE NOTE) SET BAL NET. Fig. 2 p, -(ABPP+AHB) p, Return Loss = 10 logio where : P, = teat signal power (dbm) P, = reflected s
26、ignal power (dbm) AHT = insertion loss of hybrid transmit branch AHa = insertion loss of hybrid receive branch 2.3 Net Loss 2.3.1 Definition: (Amended from ASA 65 :08:129). The net loss of a circuit, in a given direction of transmission, is the sum of all the transmission losses occurring between th
27、e two ends of the circuit minus the sum of all the transmission gains. RS-2 1 O Page 3 Copyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-EIA 210 58 = 3234600 0063237 7 = 1 RS-2 1
28、O Page 4 2.3.2 Standard: The minimum net loss from 2-wire terminals to 2-wire terminals of any circuit will be controlled by the need to meet the requirements of the Standards on Singing Margin. In practice, the net loss, from 2-wire terminals to 2-wire terminals of any circuit. will not usually be
29、less than 6 db. 2.3.3 Method of Measurement: Self evident. Measurements shall be made at a frequency of a 1000 cps. 2.4 Singing Margin 2.4.1 Definition: (ASA 66:08:297). The singing margin is the excess of loss over gain around a possible singing path at any frequency, or the minimum value of such e
30、xcess over a range of frequencies. 2.4.2 Staridard: 8 db minimum, 2.4.3 Method of Measurement: The system loop gain shall be increased until singing occurs, and then reduced until singing just ceases. The increase of loop gain at the point where singing just ceases, aver the nominal system loop gain
31、, expressed in decibels, is the singing margin. Noter Ths measurement shall be made with the two-wire brunches of the hybri sets so terminated as to prosids the minimum return losses encountered in normal service. It will zcsually be necessw to resort to trial and error n order to achieve this conit
32、on. (See Note under 2.2.2). 2.5 Talker Echo 2.5.1 Definition: (ASA 66:08:309). Talker Echo is echo which reaches the ear of the talker. Echo (ASA 65 :O8 :306) An echo is a waveform which has been reflected or otherwise returned with sufficient magnitude and delay to be perceived in some manner as a
33、wave distinct from that directly transmitted. Note: Echoes are frequently measured in db relative to the drectly transmitted wave. 2.5.2 Standard: The Permissible Tallcer Echo is dependent on the round-trip transmission time. In Communication Systems comprised entirely of microwave-derived circuits,
34、 and having a total length not in excess of 1000 miles, the value of the round-trip transmission time is so small that the requirements on Singing Margin completely outweigh those for Talker Echo,. Consequently, for such systems, it is not necessary to set a standard for Talker Echo, since it will a
35、lways fall well below the permissible value, so long a8 the standard on Singing Margin is met. Fur all other systems, the following Standard shall apply: The permissible Talker Echo is dependent on the round-trip transmission time. It has been determined statistically that the average talker is tole
36、rant of an Echo Loss which falls within the limits of the following table, for frequencies within the Echo Range: a Round-trip Transmission Time ( millisecs.) O 20 40 60 80 100 Echo Loss (db below transmitted wave) 1.4 11.1 17.7 . 22.7 27.2 30.9 Total round-trip transmission time is the sum of the d
37、elays due to line extensions, multiplex equipment, R.F. equipment, and propagation. The delays due to line extensions and Mux. and R.F. equipment are dependent on the system design, while the propagation in free space is given by: X Ooo 186,000 = .o11 miiiisecs/miie (approx.) TD = e Figure 3 shows t
38、he relationship of Echo loss, based on the above table, to round-trip transmis- sion time. Copyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-EIA 210 58 3234600 O063240 5 The trans
39、mit pair shall be connected to the other input of the recording or indicating device and through a switching device to a test signal of adjustable frequency and having a power level equal to that of the Telephone Channel Test Signal. The recording or indicating device must have an equal delay in eac
40、h of the two recording paths, and the delay of the amplifier must be small compared to the delay to be measured, The round-trip transmission time is then given by the delay from the start of a transmitted tone burst to the start of the corresponding echo tone burst as read directly from the recordin
41、g or I e indicating device. RS-2 1 O Page 5 Fig. 3 O 20 40 60 00 100 ROUND-TRIP TRANSMISSION TIME (MILLISECONDS) 2.5.3 Method of Measurement: a) ROUND-TRIP TRANSMISSION TIME See Figure 4, The receive and transmit pairs shall be disconnected from the hybrid, The receive pair shall be connected to an
42、amplifier of sufficient gain to operate one input of a dual trace recording or indicating device. The amplifier input impedance shall be such as to properly terminate the receive pair. I I + TR RECORDER OR - TERM. RES. Fig. 4 % SIGNAL TEST 7- . Copyright Telecommunications Industry Association Provi
43、ded by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-EIA 230 58 = 3234600 0063243 7 RS.2 1 O Page 4 Note (1) : If the echo signal k of such a low level Loop Leakage Resistance is the DC resistance presented to the signaling portion of th
44、e Terminating Set by the wire line, with the far end of the wire line open-circuited. 3.2.2 Standard: 15,000 ohms minimum. 3.3 Ringing Current 3.3.1 Definition: Ringing Current is that current which is applied to a telephone line for the purpose of actuating a ringer or other device at the far end o
45、f the line, the ultimate purpose of which is to attract the attention of an operator or a telephone user. 3.3.2 Standard: In view of the wide range of frequencies and type of signals currently in use in the industry it is not desirable to set a standard. However, in view of the large usage of 20 cps
46、 ringing current at the present time, the following standard for 20 cps ringing current is suggested : Terminating Sets intended for use with 20 cps ringing current shall operate on a minimum of 60 volts RMS at 20 cpa measured at the line terminals of the Terminating Set. 3.4 Ringing Voltage 3.4.1 D
47、efinition: Ringing Voltage is the ringing-frequency voltage developed across the line due to the application of Ringing Current to the line. 3.4.2 Standard: The maximum ringing voltage applied to the line from the terminating equip- ment shall not exceed that value which will cause operation of prot
48、ection on the line, or cause damage to, or faulty operation of other equipment connected to the line. In addition, the ringing voltage and waveform shall not be such as to induce unreasonable interference into other circuits and services. 3.5 Impedance of Devices Responding to.Ringing 3.5.1 Definiti
49、on: (Self Evident). 3.5.2 Standard: The impedance of devices within the Terminating Equipment which respond to Ringing shall be not less than 2600 ohms at the ringing frequency. Copyright Telecommunications Industry Association Provided by IHS under license with EIANot for ResaleNo reproduction or networking permitted without license from IHS-,-,- EIA 210 58 m 3234b00 O063244 2 m RS-2 16 Page O 3.6 Battery Voltage 3.6.1 Definition: S
