TELECOM Digest Thu, 30 Aug 90 19:27:00 CDT E-Series Recommendations Inside This Issue: Moderator: Patrick A. Townson E-Series Recommendations Excerpts [Joel M. Snyder] ---------------------------------------------------------------------- Date: Thu, 30 Aug 1990 01:13:43 MST From: Subject: E Series Recommendations Excerpts - for Edification and Emusement Here are Interesting Facts and Figures entered from the CCITT Recommendations of 1988. There are errata for these Recommendations, but I have not applied them to these! Also, my typing skills are not perfect. Note: these are all excerpts, and quotes. I have left out substantial text, and am including only some of the more interesting tidbits. If you are really interested, make sure you get the entire text! Things in [] are my comments. ------------------------ From Recommendation E.180, Technical Characteristics of Tones for the Telephone Service [I left out all the stuff about dB levels of tones, mostly because it was accompanied by a lot of graphs] Dial Tone: It is recommended that dial tone be either a single frequency tone in the range 400 to 450 Hz, or a combined tone composed of up to three frequencies, with at least one frequency in each of the ranges 340-425 Hz and 400-450 Hz. The difference between any two frequencies should be at least 25 Hz. When adopting a new single frequency dial tone, Administrations are recommended to use 425 Hz. Ringing Tone: Ringing tone is a slow period tone, in which the tone period is shorter than the silent period. The recommended limits for the tone period (including tolerances) are from 0.67 to 1.5 seconds. The recommended limits for the silent period separating two tone periods are 3 to 5 seconds. The first tone period should start as soon as possible after the called subscriber's line has been found. The ringing tone cadence should be similar to the cadence used for applying ringing current to the called subscriber's telephone set, but these two cadences need not be synchronized. [It goes on to discuss frequencies for ringing tone] Busy Tone and Congestion Tone: The subscriber busy tone and the equipment or circuit group congestion tone are quick period tones in which the tone period is theoretically equal to the silent period. The total duration of a complete cycle (tone period E + silent period S) should be between 300 and 1100 milliseconds. The ration E/S of the tone period to the silent period should be between .67 and 1.5. The busy tone and the congestion tone can be identical, but a distinction is desirable. Special Information Tone: [This is that tri-tone we've been talking about lately.] The special information tone has a tone period that consists of three successive tone signals, each lasting for 330 +- 70 milliseconds. Between these tone signals may be a gap of up to 30 milliseconds. The frequencies used for the three tone signals are 950 Hz; 1400 Hz; 1800 Hz (all +-50 Hz) sent in that order. After the special information tone is a 1000 millisecond (+-250 ms) silent period. [ Other tones are described: the warning tone to indicate that a conversation is being recorded, the payphone recognition tone, the call waiting tone (400 to 450 Hz for 300 to 500 ms, followed by 8 to 10 sec silence OR 400 to 450 Hz on for 100 to 200 ms, silent for 100 to 200 ms, and on for 100 to 200 ms, followed by 8 to 10 sec silence); and caller waiting tone (you didn't know we had one of those, did you? It's supposed to be similar to ringing, so if you don't know what it is, it sounds like ringing)] ------------- Supplement 2 to Fascicle II.2 (E-series Recommendations) This is a really interesting one. It gives the frequencies and cadences for dial tones, ringing tones, busy tones, etc. around the world. Example: In Finland, the dial tone is a 425 Hz tone generated as three pulses of .2 sec length separated by two pulses of .3 sec length, followed by .8 second silence. In El Salvador, the busy tone is 1/3 second tones of 425 Hz separated by 1/3 seconds of silence. In the US, the "special information tone" is three 1/3 second pulses without pause at 950, 1400, and 1800 Hz. God only knows how much of this is accurate, of course. I'm sure our Finnish readers will be able to comment on the first. ------------------- Recommendation E.123 Notation for National and International Telephone Numbers 1.1 The international number should be printed below the national number, with corresponding digits lined up one under the other to facilitate understanding of the composition of the international number as showd in the examples in 1.3 and 1.4 below. 1.2 The words "National" and "International" in the appropriate langauge should be placed to the left of the national and international numbers, and these should be separated by a horizontal line. 1.3 Either the symbol for the telephone given in Rec. E.121 or the word "Telephone" in the appropriate langauge should be placed to the left of (or above) the national and international numbers (to avoid confusion with other letterhead numbers.) The + (plus) signifies the international prefix. Example: National (0607) 123 4567 Telephone -------------------------------------- International +22 607 123 4567 1.4 Because the countries of World Numbering >one 1 (North America) have the country code 1, the same number as is used for the trunk prefix, and because dialing between these countries is the same as long-distance dialing within them, subscriber difficulties are avoided by using an alternative notation that has been found superior for use within those countries and equally good for subscribers in other countries dialing to Zone 1. Example: Within N. Amer. zone (302) 123 4567 Telephone -------------------------------------- International +1 302 123 4567 1.5 If it is desirable to write only the international number, it should be written in the form: Telephone International +22 607 123 4567 1.6 [abbreviated: Extensions use the word "ext.", like this:] National (0607) 123 4567 Telephone -------------------------------------- ext. 876 International +22 607 123 4567 2. Classes of symbols [not too exciting, but there is one interesting part:] 4.4 Multiple numbers without automatic search For a subscriber with multiple numbers who does not have automatic search, the symbol / (oblique stroke, solidus, or slant) may be used to separate the alternative numbers. Example A: (0607) 123 4567 / 123 7272 / 627 1876 It is especially important that there be a space on either side of the symbol /. When it is desired to abbreviate the alternative numbers, and they are consecutive, only the last digit should be shown for alternative numbers: Example B: (0607) 123 4567/8/9 It is especially important that there be no space on either side of the symbol /. 4.6 Symbol to indicate the existence of an additional dial tone. [Essentially: use a tilde (~), or as close as you can get to the graphical representation of a full cycle of the sine wave. Don't use a hyphen, and put spaces around it so it won't be confused for a hyphen. 7. Facsimile number notation The printed format for facsimile numbers should follow the conventions set forth for voice telephone numbers except that facsimile numbers should be clearly labeled with the upper case letters FAX printed to the left of the numbers as illustrated here: National (0607) 123 4567 FAX -------------------------------------- International +22 607 123 4567 -------------------------- E.163 and E.164 should be familiar to any of you ISDN hackers -- they're the numbering plan for the international telephone service, which includes all of the Country Codes. Some of these have appeared before in this forum. I won't retype them. --------------------------- E.161 Arrangement of Figures, Letters, and Symbols on telephones and other devices that can be used for gaining access to a telephone network: 1. Use of figures and letters in telephone numbers [Don't use figures. Use numbers] 2. Rotary dials. [There's a picture there, which looks like our standard rotary dial, sort of. The holes are numbered from 1 to 0, with the letters as follows: 1 (none) 2 ABC 3 DEF 4 GHI 5 JKL 6 MN 7 PRS 8 TUV 9 WXY 0 OQ ] 3. Pushbuttons or keys 3.1 10 buttons [More figures. Essentially says: 1 2 3 4 5 6 7 8 9 0 Also, if you HAVE to, you can do: 1 2 3 4 5 6 7 8 9 0 or 1 2 3 4 5 6 7 8 9 0 with a note: "User dialing performance on these special arrays is slightly inferior to that on the standard array given above."] The letters are the same as on rotary dials; note the letter O is on the number 0, and not on the number 6. 3.2 12 buttons [Add * and # in the usual places. There's this big picture of the *, and it will be known as the "star." Also, there's two big pictures of the #, which I'll try to reproduce here: X X X X XXXXXXXXXXXXXXXXXXXXX X X X X X X X X X X X X XXXXXXXXXXXXXXXXXXXXX X X X X The length of the long bar is b, and the length of the stub after the cross (two Xs in my picture) is called a. The angle is called alpha. In Europe, alpha = 90 degrees with a/b = 0.08 In North America, alpha = 80 degrees with a/b close to the upper limit of 0.18 This symbol will be known as the square. [There's more, noting that you shouldn't color the pushbuttons different colors, and you should have a register recall pushbutton instead of using switchhook flash.] ------------------- Recommendation E.114 Supply of Lists of Subscribers 1. Each Administration shall supply by mutual agreement and free of charge to the Administrations with which a telephone service exists a sufficient number of copies of its lists of subscribers for official use. 2. A subscriber wishing to obtain a telephone directory of another country must apply to his own Administration. If an application for one of its telephone directories is received directly by an Administration by a subscriber in a foreign country, the receiving Administration shall inform the subscriber that such requests should be addressed to his own Administration. 3. An Administration which has supplied telephone directories of its own country to another Administration for distribution to subscribers shall indicate the sale price of the directories plus any postal charges (in principle expressed in gold francs) for the use of the receiving Administration. 4. Accounting concerning the supply of such directories for subscribers' use shall be conducted according to the usual procedure followed between Administrations (see Recommendation D.170) unless Administrations, by mutual agreement, elect to forego such accounting. [typed in its entirety] -------------- Recommendation T.20, Standardized Test Chart for Facsimile Transmissions You probably have heard of this test chart, since that's what your FAX manufacturer used to propose the incredibly high rate of transmission you never see on your own equipment. The funny part of this one is that the test chart has some half tones, some lines, and other stuff, but the center is a picture of a small child: "Argentine Boy." One wonders how long they had to argue over the picture... T.21 is a second test chart, which has texts in English, French, Spanish, Chinese, Arabic, and Russion. ------------------------- Recommendation E.117 Provisions concerning the device substituting a subscriber in his absence 1. Precautions will have to be taken by the Administrations to warn callers of the presence on the called subscriber's line of a device substituting him in his absence: a. Devices of this type should be indicated in the telephone directories by means of a special sign [...] [Here, I'll try to describe the sign. It looks very much like a backwards Q: There is a large circle, larger than any other character in the type face, with a small stroke through it, going South-West. The stroke doesn't go quite to the center, and extends out about as far as it extends in. I bet the angle is exactly 45 degrees (or 225, if you want to think of it that way).] b. Administrations should invite the owners or renters of such equipment to mention the fact on their letterheads by means of a printed indication. 2. To facilitate the disposal of international traffic on a device of this type, the Administrations should, when consenting to this equipment, insist that it complies with the essential conditions set out in the following Annex. (end of Recommendation, beginning of Annex A to Recommendation E.117 A.1 Operating Conditions A.1.1 Delay in Answering The ringing current from the telephone exchange should be premitted to operate the telephone bell for at least three seconds but not for more than ten seconds before the call is answered by the apparatus. This will enable the call to be answered in the normal way in those countries which wish to provide for such a facility. The timing of this interval (three to ten seconds) should be independent of the periodicity or the duration of the ringing current. A.1.2 Normal conditions for metering and supervision In answering a call the apparatus should loop the subscriber's line and should give the normal conditions for control of metering and for supervision as with a normal subscriber's installation. The disconnection of the apparatus should break the loop on the subscriber's line. A.1.3 Announcement of the presence of the apparatus A.1.3.1 The presence of the apparatus should be indicated to the calling party by means of a verbal announcement following, in principle, immediately on the closing of the loop on the subscriber's line. A.1.3.2 This verbal announcement should include, in particular, the following: - first, that it is a reconding apparatus; - the subscriber's name or business style; - the subscriber's number and particulars of the locality (e.g., Geneva, St. Moritz, etc.) - clear instructions as to the functioning of the apparatus (whether a message may be recorded, and if so, the moment when the message may be recorded and the maximum duration of the recording). A.2 Signalling conditions A.2.1 Avoidance of interference from signalling frequencies The correct functioning of the apparatus should not depend upon (nor be affected to any extent by) the sending or receiving of signalling frequencies used in the telephone system or specially generated in the apparatus. A.2.2. Avoidance of interference with national signalling systems by the tones transmitted by the apparatus To avoid interference with the national signalling system of a country by the tones transmitted by the apparatus over the network of that country, it is recommended that: - the transmission of tones should be in short pulses and not a continuous transmission; - the tones should not be composed of a single frequency, but should be a mixture of at least two frequencies, so that the guard circuit of the signal receiver of the corresponding country, where there would be a risk of interference, may operate. For this purpose, the choice of the following frequency-combinations should be avoided: 2040 and 2400 Hz 600 and 750 Hz 1200 and 1600 Hz 500 and 20 Hz 1000 and 20 Hz A.3 Transmission Conditions Any recording apparatus which takes the place of the called subscriber should give a level and quality of speech comparable to that given when the station is used by a person. ------------------------------ End of TELECOM Digest Special: E-Series Recommendations ******************************