euatdt@euas11g.ericsson.se (Torsten Dahlkvist) (08/21/89)
Since the discussion about Calling Number Identification seems to have started again, I feel a need to say my word on the subject even though I've posted some of this before. Apologies to those who feel annoyed about this. The Calling Number Identification facility (CNI) of ISDN is a nice example of the new features the all-digital communication technology offers us. Some feel this to be an intrusion on their privacy, but as the moderator pointed out in his footnote to <telecom-v09i0309m05@vector.dallas.tx.us>, CNI has long been available to the telcos, the Police and other "worthy" institutions. In the U.S. they are even, apparently, forced by law to hand this on in full (address and all) to other telcos for billing. Now that it's being offered to the general public the only main difference lies in that more people are getting it. Several readers have pointed out the need for a way for users to cancel CNI transfer in certain cases, like the battered woman calling to tell her kids she's all right. In <telecom-v09i0309m04@vector.dallas.tx.us> Bob Frankston states that: > the caller must be provided with safeguards. It is not sufficient > to say that prefixing a call with *999 provides privacy -- it must be > possible to make that a default on a line." To clarify things a bit I'd like to point out a few fundamentals about CNI in ISDN as proposed by CCITT and implemented by several manufacturers. If ATT has chosen to go for a full implementation I do not know. If they haven't, I'll leave it up to them to defend their decisions. 1) CNI is always sent from the originating caller's exchange to the exchange of the destination. 2) With the CNI is included an indication telling if the caller wants this info to be sent on to the callee or to stop at the telco. 3) The "no CNI" indicator is controlled by: a) what is explicitly ordered for this call, b) the default for this line, c) the default for this telco, If the caller dials a special code when setting up his call, or if he's using a feature-phone which can be pre-programmed to do it automatically, he can select to - on a call-at-a-time basis - override the default for the line. If no special code is given, the default for the line is used. This would enable customers with un-listed numbers to guard their privacy. Using a) above, they can still send CNI to trusted people. If no default is specified for the line, the default set by the telco is used as a last resort. 4) The called subscriber in his turn must subscribe to CNI in order for his exchange to send it on to him. 5) For "special" subscribers (Police, Fire, telco offices) the exchange can be programmed to give CNI at all times regardless of what the caller may have specified. This allows continuation of emergency services as provided today. As you can see, there is no guarantee in this that the FBI or CIA will not tap into the data stream between the exchanges to see exactly who is calling the Russian Embassy. The situation is exactly the same in this aspect as it has been for many years. Also, there is no way to stop a salesperson (or obscene caller) from using the suppression facility to avoid beeing identified. In the end you may find yourself where you only answer calls identified as beeing from your friends, or at least beeing identified so that you can get back at them if you dislike their message. In <telecom-v09i0309m01@vector.dallas.tx.us> Charles Daffinger requests some means of identification that would not hazard the privacy of un-listed subscribers. Bearing in mind what I've said above about the suppression facility, the non-listed subscriber who wants to identify himself without revealing his number (or the regular user who wants to add more personality to his calls) can use the User-User-Info facility, UUI. This comes in a number of varieties in ISDN, but what I was thinking of right now is the Call Setup version where a text of up to 32 characters (bytes, really) can be programmed into the callers feature-phone and is transferred on each outgoing call. This can be displayed along with or instead of the CNI, as the case may be, and allows you to send your name, company name or just a funny note of your choice to the other party. The telco charges for this transfer, of course, since the info goes there and can be read even if he doesn't answer. Still, this, along with CNI, may provide the cheapest means by far for students-in-distress to call their parents and say "call me back at this number". There seems to be some misunderstanding on the net of the full implications of ISDN on phoning and datacomm. For example, in <telecom-v09i0311m02@vector.dallas.tx.us> Mike Morris worried that if he used his second line to make an outgoing call the number normally leading to his modem line would be sent to the other party and either not be recognized or later incorectly used to call back to him. But in ISDN you will not be using your old modem - it will not fit. Instead you will need to buy a new "ISDN-modem" which will - at first - be rather costly but which will give you a number of nice features like high-quality data transfer at 64 kb/s. And built-into the ISDN concept is the call-type identifier which ensures that the modem will only answer datacomm-calls and the phone will only answer speech connections. They may share the same line and the same number, they will still not interfere with each other. If you get a computer with a built-in ISDN card you may find that it gives you both speech and data capability so that you may use the computer both as a BBS and a feature-phone. Incoming calls identified as "phone" will start it ringing and urge you to pick up the receiver while calls identified as "data" will silently start the logon routine. Of course, trivialities like baud rates, parity and such are handled automatically in the call-setup so that the connection takes place only if both ends manage to agree on how to communicate. No need to scan carrier frequencies up and down at different speeds to try to find a match. Since the customer access to ISDN is 2B+D, every subscriber in reality gets a two-line system. This is one of the reasons why telcos are pushing ISDN in spite of the cost. They can meet the increasing demand for second phone lines to homes and businesses without digging up the street. You just go ISDN, they install some hardware at your premises and change your phones (and modems) (you pay through the nose for all the new features, of course) and then it's done. This means you can have two different phone calls going on at the same time. Or two datacomm connections. Or one of each. Your line will not be busy until both B-channels are in use. Since the exchange is necessarily all-digital, call forwarding and such facilities are trivial to include. In ISDN this is used to tie several numbers to the same line. In the incoming call-setup info a field called "Called Party Number" tells which number the caller dialled and you can program your phones (and modems) to accept calls to certain numbers only. This way, you can give the kids their own phone and their own number by simply having another number tied to your line. You then decide for each phone which number(s) to enable in it. Another entry in the feature-phone is the "Given Calling Patry Number" field. Since you have several numbers tied to one physical line, you need to specify which of these numbers is to be used for CNI when you make an outgoing call. This means that if you have four phones in your house - one in the kitchen, one in the kids' room, one in your den and one in the living-room - you could tie a set of three numbers to this installation, say 101, 102 and 103. You then program the phone in the kitchen to use 101 for both outgoing and incoming calls. The phone in your den uses 102 and the kids get 103. The phone in the living-room, however, is not obviously the "property" of either of you so maybe you program it to answer to both 101 and 102 while giving it's own identity as 101 when calling out. That way, when you make a call from the den, your wife calls from the kitchen or the kids call from their room, the party at the other end always gets the correct number to use when returning the call. In the living-room the phone will ring for either you or your wife, while outgoing calls will look as if they are made by her. (Ladies: please forgive me for this very blatantly sexist family set-up. It's just an example to illustrate the facilities of ISDN, o.k? :-) Maybe you want to keep one of the numbers un-listed and have the others listed. No problem. Just remember not to program any of the phones to send the non-listed number as CNI. You could still let all phones answer to that number if you want to. Or just some. Your choice. Maybe you are in the living-room about to make a call when the phone rings. You see from the CNI and UUI that it is for your wife, so you press the "kill" button and your phone stops ringing. You then lift the receiver and the phone automatically grabs the other B-channel to make an outgoing call (if the kids aren't already using it in which case you will get a "No B-channel available" text message and you'll just have to wait :-) The phone in the kitchen still rings and will do so until your wife answers (or presses "kill" as well :-) or the calling party hangs up. All questions on the practical aspects of ISDN use are welcome by E-mail. Any interesting points will be summarised and posted. /Torsten Additional disclaimer: What I've said here is merely my personal interpretation of what I consider to be "common knowledge" in the field of ISDN. I do not in any way represent ERICSSON in these matters. If anyone has questions regarding ERICSSON's ISDN programme I will immediately refer them to some suitable sales-creature over at the main offices. Torsten Dahlkvist ! "I am not now, nor have I ever ELLEMTEL Telecommunication Laboratories ! been, intimately related to P.O. Box 1505, S-125 25 ALVSJO, SWEDEN ! Dweezil Zappa!" Tel: +46 8 727 3788 ! - "Wierd" Al Yankowitz [Moderator's Note: My sincere thanks for an excellent presentation to the Digest readers! PT]