scotts@bu-it.BU.EDU (01/03/89)
I have compiled some more information about the SACs for your edification. These include 700, 800, and 900. Most telephone users from the United States are quite familiar with 800 service. A number that they dial and incur NO charge (not even message units in most [all?] areas). Then there is 900 service, which is most people perceive as 'value added', i.e. you pay more for the information than for the transport of the call. These vary typically from 35 cents to a few dollars for either a timed service, or a 'as long as you like' duration-sensitive service. There are two sub-species of 900 service, AT&T and "everybody else". Finally there is 700 service, which many people remember as Alliance Teleconferencing. This is the third "canonical" SAC. With few limitations, this SAC is given over to the IEC entirely. Let's look at these in more detail: 800 service is offered by various IECs. Each NXX in the 800 SAC is assigned to a given carrier, who is responsible for assigning numbers from that block to customers, and providing 10 digit translation. When you as Joe Customer dial 1-800-222-1234 (made up number, please don't bother them) it will initiate the following sequence: 1. If you are in an Electronic Office (DMS-100, DMS-200, 1A ESS, #5 ESS) the 800-222 will be translated to "AT&T" and search for an opening in a trunk group marked for 800 origination. Should none be found, bump to step 3 2. If you are in a non-electronic office (SXS, XB, and some flavors of ESS), it will go to the access tandem that you're office 'homes' on, where 800-222 will be translated to "AT&T" [note that if at this point, the number doesn't have a translation, you will get a "lose" recording from the CO] 3. Find a trunk in a trunk group marked for 800 origination. Should none be found, give the customer a recording "Due to network congestion, your 800 call could not be completed" or die, or whatever. (Depends on phase of moon, etc.) 4. The end office will the send the following pulse-strea (in MF): KP + II + 3/10D + ST + KP + 800 222 1234 + ST (note that this is a simplification, there are some fine points of ANI spills that are beyond the scope of this article) II = 2 information digits ... typical values are: 00 normal ANI .. 10 digits follow 01 ONI line ... NPA follows 02 ANI failure ... NPA follows 3/10D = 3 or 10 digits. Either the NPA, or the entire 10 digit number. KP and ST are control tones 5. The carrier receives all of this (and probably throws the ANI into the bit bucket) and translates the 800 number to what's called a PTN, or Plant Test Number. For Example, 617-555-9111. Then, the call is routed AS IF the customer had dialed that 10 digit number. Of course, the billing data is marked as an 800 call, so the subscriber receiving th call pays the appropriate amount. 900 Service. As I mentioned earlier there are two flavors of 900 service, AT&T, and "Everybody Else". Everybody else is handled exactly as 800 service above, except the IEC will probably use the ANI information to send you a bill. (Either directly, or through your BOC, each situation governed by applicable tarrifs and contractual arrangements between the IEC and the BOC) AT&T 900 is a curious monster indeed. It was designed as a "mass termination" service. When you dial a 900 # by AT&T (such as the "hear space shuttle mission audio" number) you get routed to one of twelve "nodes" strewn throughout the country. These nodes are each capable of terminating 9,000 calls >PER SECOND<. There are several options available, where the customer and/or the IP pay for all/part of the call. The big difference between 800 and AT&T 900 is >NOT< "who pays for the call" (there are free 900 numbers) but "how many people can it handle at once". The IP is responsible for providing program audio. AT&T is prohibited from providing audio-program services (i.e. tape recorded messages) [As with any rule, there are exceptions to these as well] The last SAC we'll deal with is 700. I've seen ads on late-nite television for Group Access Bridging service (GAB) under 700 numbers, with a elephantine dialing sequence. The one that comes to mind is 10041-1-700-777-7777. [I make no guarantee about the quality or availability of this service. I don't even know if it still exists.] If you were to dial 1-700-555-4141 you will hear a recording announcing your Equal-Access carrier. (Some carriers ignore the last four digits, and any 700-555 number will give the announcement). This is signalled the same as 800 service, and may or may not be billed ENTIRELY at the discretion of the IEC. In New York, under PSC tarrif you can order 900 and/or 700 blocking as well as 976, 970, 550, and 540 blocking in various (but not entirely orthoganal) combinations. What in ONE carrier might be a customer service hotline (Dial 1-700-I AM LOST) might for another be a revenue product. There is LITTLE standardization of 700 usage from IEC to IEC. The one last dialing pattern that is worth mentioning is what's called, "cut through dialing". Try dialing 10220#. If Western Union comes to your town, you'll get a FG-A style dial tone. Presumably if you had a Western Union "Calling Card" [I don't know their term for it] you could dial a call. (If someone DOES have WU service, could they please check this out for me?) Glossary: ANI - Automatic Number Identification. An MF sequence that identifies your line for toll billing information. Often confused with ANAC (Automatic Number Announcemnt Circuit) which reads your number back in a synthesised voice. BOC - Bell Operating Company. A often misused term (even in this very article :-) that in general usage means, "Your local exchange carrier." Since most of the telephones in the country are served by what used to be the Bell system, we tend to use the term. The proper term in this case, however IS "Exchange Carrier [EC]" They provide service within your LATA. FG-A - Feature Group A. Line Side termination for Long Distance carriers. The old 555-1234 for Widget Telephone Company then dial an access code and the number style dialing is called FG-A. FG-B - Feature Group B. Trunk Side termination for Long Distance carriers. (aka ENFIA B). 950 service. This is LATA wide service, and doesn't cost the customer message units. ANI is only provided when the trunks terinate in the End Office (as opposed to an access tandem). FG-D - Feature Group D. Trunk Side termination. Provides 10xxx dialing, 1+ pre-subscription dialing, and Equal Access 800/900 service. Only available in electronic offices and some 5XB offices (through a beastie called an Adjunct Frame.) GAB - Group Audio Bridging. Where several people call the same number, to talk to other people calling the same number. "Party" or "Chat" lines. IEC - Inter-Exchange Carrier. Someone who actually carries calls from place to place. AT&T, Sprint, MCI are all IECs. IP - Information Provider. Someone who sells a value-added service over the telephone. Where you pay for the INFORMATION you're receiving, as well as the cost of TRANSPORT of the call. NXX - Notation convention for what used to be called a "prefix". N represents the digits 2 through 9, and X represents the digits 0 through 9. There are 800 valid NXX combinations, but some are reserved for local use. (411 for Directory, 611 for Repair Bureau, 911 for emergency, etc.) ONI - Operator Number Identification. In areas with some styles of party-line service, the CO cannot tell who you are, and the operator will come on and say, "What number are you calling from?". You can lie, they have to trust you. They MAY know which PREFIX you're coming from, though. PTN - Plant Test Number. A regular 10 digit number assigned with your inward WATS line. This may NOT be a 'dialable' number from the local CO. (A friend has a WATS line in Amherst, MA [413-549, #5 ESS] and you cannot dial the PTN locally, but you can if you come in on a toll trunk.) SAC - Special Area Code. Bellcore speak for area codes that aren't really places, but classes of service.
levin@uunet.UU.NET (Joel B Levin) (01/10/89)
In article <telecom-v09i0008m03@vector.UUCP> scotts@bu-it.BU.EDU writes: |AT&T 900 is a curious monster indeed. It was designed as a "mass |termination" service. When you dial a 900 # by AT&T (such as the |"hear space shuttle mission audio" number) you get routed to one of |twelve "nodes" strewn throughout the country. These nodes are each |capable of terminating 9,000 calls >PER SECOND<. . . . This is also the AT&T service which allows those obnoxious television "polls" ("dial this number to vote yes, this other number to vote no, and by the way this costs fifty cents"). |The one last dialing pattern that is worth mentioning is what's |called, "cut through dialing". Try dialing 10220#. If Western Union |comes to your town, you'll get a FG-A style dial tone. . . . I haven't tried for a long time, but in Nashua NH (603-880-) this did work for Sprint, i.e. 10777 + # would get you the same peculiar dial tone that their dial-in access number would, expecting you to reply with your access code and destination number. This was convenient because you could reach their customer service by dialling the above followed by the special 6-digit numbers (without access codes). /JBL == UUCP: {backbone}!bbn!levin POTS: (617) 873-3463 INTERNET: levin@bbn.com