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) EIA 210 58 = 32346
2、00 0063235 1 NOTICE EIA standards are adopted in the public interest and are designed to eliminate misunder- standings between the 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 sta
3、nd- ards does not in any respect preclude any member or non-member of EIA from manufacturing or selling products not conforming to 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 p
4、atents on articles, materiais or . processes,-,By such action, the Association does not assume any liability to any patent owner, nor does it assume any obligation whatever ,to parties adopting the recommended standards or practices. Published by ELECTRONIC INDUSTRI ES ASSOCIATION Engineering Depart
5、ment 2001 Eye Street, N.W., Washington, D. C. 20006 Copyright 1968 by Electronic Indiutrfem AssocMion Ali rfphta renerved EIA 210 58 W 3234600 0063236 3 - RS-2 1 O Page 1 Terminating and Signaling Equipment for Microwave Communication Systems Part I: Telephone Equipment (From Standards Proposal Nos.
6、 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 Singing Margin 2.5 Talker Echo 2.6 Insertion Lo
7、ss 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 Ringing 3.6 Battery Voltage 3.7 Pulse Signalin
8、g 3.8 Dial Pulsing Speed 3.9 Per Cent Break 3.10 Signaling Pulse Distortion 4. SUPPLEMENTARY DEFINITIONS 4.1 Definitions from Other Sources 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-
9、phone Service. Subsequent parts will cover such services as Data Transmission, Remote Control, 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
10、 practices to a single standard for Terminating and Signaling equipment for Telephone Service. 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 considerat
11、ions is the achievement of a common acceptance of terms and . their definitions. Wherever 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 Com
12、mittee. A list of applicable terms, their sponsors and reference, is included in this Standard. 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 i
13、ndividuully in order to ascertain the exact equipment arrangements which must be supplied 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 syste
14、m. 2.1.2 Standard: Not applicable. 2.1.3 Method of Measurement: To measure the net system 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 t
15、o that of the Telephone Channel Test Signal at this point in the system, shall be applied 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
16、 expressed in db. TR REC 7- I MICROWAVE + MULTIPLEX -=- TERMINATION EQUIPMENT a-+ ./ REC 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 t
17、he reflected wave. More broadly, the return loss is a measure of the dissimilarity between two impedances, being equal to the scalar value of the reciprocal of the reflection coefficient, and hence being expressed by the formula: - y- -_ EIA 210 58 3234600 O063238 7 W 201og10 I g: :E: 1 db where Z1
18、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 the con- nected equipment (such as telephone sets, cable circuits, Central Office equi
19、pment, 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 loss at which the circuit can be operated and still meet the requirements for Singing M
20、argin 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 of the Telephone Channel Test Signal at this point in the system shall be applied to
21、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 reflected signal power (db) - the sum of the insertion losses of the Transmit and Rec
22、eive 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 frequency at which the Return Loss has its lowest value. It will usually be necessary to re
23、sort 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 signal power (dbm) AHT = insertion loss of hybrid transmit branch AHa = insertion los
24、s 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 the two ends of the circuit minus the sum of all the transmission gains. RS-2 1 O Page
25、 3 EIA 210 58 = 3234600 0063237 7 = 1 RS-2 1 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 t
26、erminals of any circuit. will not usually be 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
27、any frequency, or the minimum value of such excess 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 j
28、ust ceases, aver the nominal system loop gain, 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
29、trial and error n order to achieve this coniton. (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 a
30、nd delay to be perceived in some manner as a 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 comp
31、rised entirely of microwave-derived circuits, 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 se
32、t a standard for Talker Echo, since it will always 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
33、statistically that the average talker is tolerant 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 rou
34、nd-trip transmission time is the sum of the delays 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 mii
35、iisecs/miie (approx.) TD = e Figure 3 shows the relationship of Echo loss, based on the above table, to round-trip transmis- sion time. EIA 210 58 3234600 O063240 5 The transmit pair shall be connected to the other input of the recording or indicating device and through a switching device to a test
36、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 each of the two recording paths, and the delay of the amplifier must be small compared to the delay to be measured, The round-tri
37、p 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 recording 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
38、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 amplifier of sufficient gain to operate one input of a dual trace recording or indicating device. The amplifier input impedanc
39、e shall be such as to properly terminate the receive pair. I I + TR RECORDER OR - TERM. RES. Fig. 4 % SIGNAL TEST 7- . 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
40、 the 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 en
41、d of 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
42、cps 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.
43、1 Definition: 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 p
44、rotection 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 Defin
45、ition: (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. - EIA 210 58 m 3234b00 O063244 2 m RS-2 16 Page O 3.6 Battery Voltage 3.6.1 Definition: Signaling. Battery. is that sou
46、rce of direct current which provides energizing current for operation of signaling relays and associated equipment. 3.6.2 Standard: Signaling Battery voltage supplied to the battery terminals of the Terminating Equipment shall be held within the following limits, from minimum to maximum load conditi
47、ons: a) For loop pulsing: 48 volts f 3 volts DC positive grounded 24 volts =r: 2 volts DC positive grounded b) For DC signaling not requiring loop pulsing : 48 volts f 10 volts DC positive grounded 24 volts f 4 volts DC positive grounded Signaling and Talking Power may, where convenient, be supplied
48、 from a common source. In this case, the supply must meet the requirements of both Standards. 3.7 Pulse Signaling 3.7.1 Definition: Pulse Signaling is that form of signaling in which a steady state condition, such as a direct current or a tone, is pulsed in accordance with a prescribed code, as for
49、example in telephone dialing. The following Standards for pulse signaling apply to all of the circuits defined below, and are based on contemporary practice for telephone dial signaling. In each case, signaling is accom- plished by pulsing a direct current. a) Loop: A loop signaling circuit is one in which the pulses are delivered to, or received from, a circuit on a metallic pair, normally the talking pair. Ground, if present, is not part of the signal- ing path. b) Simplex : A simplex dial signaling circuit is one in which the pulses are delivered to or received from a circ
