lairdb@crash.cts.com (Laird P. Broadfield) (06/18/91)
Okay, here it is:
Can you have two cellphones (I guess you can't call them "desk sets",
can you?) on the same number? I'm sure you could get ring-no-answer
and busy-forward from one to another, but I'm talking about for-real
both sets on one 7digit.
What happens if they're in the same cell?
What happens if they both originate a call?
What happens if they both *answer* a call at the same time?
I can mentally make a case that this would work, but I can also make a
good case that it wouldn't. It all depends on how the interaction
between the 7digit and the ESN works; does the switching equipment
broadcast on the control channel for a particular device, or does it
say "Would anyone like to be 555-1212 today?" and listen for replies?
I'd appreciate it if one of you in-the-know people would give the
$0.05 lecture on how this all works, and/or point me toward a cellular
primer.
(P.S. U.S. West is the B carrier out here; does anybody know if they
have sales offices anywhere where bundling *is* legal?)
Laird P. Broadfield
UUCP: {ucsd, nosc}!crash!lairdb
INET: lairdb@crash.cts.com DREUBEN@eagle.wesleyan.edu (Douglas Scott Reuben) (06/20/91)
In article <telecom11.467.2@eecs.nwu.edu>, lairdb@crash.cts.com (Laird P. Broadfield) writes: > Can you have two cellphones (I guess you can't call them "desk sets", > can you?) on the same number? I'm sure you could get ring-no-answer > and busy-forward from one to another, but I'm talking about for-real > both sets on one 7digit. I think this was mentioned here about a year ago (?), and from what I have read, as well as discussions about this with people at various cell companies, you can only have ONE phone assigned to a specific phone number, ie, there can only be one valid phone #/ESN combo active in a system at a time. (Your ESN can have multiple valid numbers assigned to it, though.) The problem lies in that the ESN is "unique", ie, unless you go out of your way and copy the ESN (not too easy), the second, or "extension" phone won't work because the cellular company won't recognize the ESN. In order to place/receive a call, the cellular company does a phone number <-> ESN match check. If your phone number and ESN match with their records, you are allowed to place/receive the call. If not, your call is blocked. So if you have two phones, and you program both to have 415-555-1234 as their number, but they have different ESNs, then only the one with the valid ESN (according to the cellular company's records) will ring. The other will just sit there when someone calls, and do nothing. Some systems may even "lock out" the "invalid" ESN phone from being used even if you switch it back to a valid number at a later time. > What happens if they both originate a call? > What happens if they both *answer* a call at the same time? These are some of the reasons why there is only one phone assigned to a cell phone number, even though I think both can be circumvented. IE, let's say you DO copy your ESN from the original to the "extension" phone. So now both phones have an ESN/number match. Wouldn't both of them ring? I don't know much about the "software" that the MTSO and/or associated computers run, but would the system, seeing two phones answering the same page/call, lock both of them out? (or even lock them out after getting TWO valid ESN/number matches, if the system routinely or for some reason queries the phone(s) ? ) It seems POSSIBLE that cellular companies could offer this service, assuming they modified their software to allow for this. IE, you tell them you want to assign two different ESNs (so you don't have to copy them yourself) to the same number, and that both should ring if a call comes in. The one that picks up the call first gets to talk. If both pick up at the same time, the program will only allow one ESN to get the call, based on some pre-arranged priority system. The system would be similar for Call-Waiting, and Nationlink/FMR, but let's not get into roaming! ;) > I can mentally make a case that this would work, but I can also make a > good case that it wouldn't. It all depends on how the interaction > between the 7digit and the ESN works; does the switching equipment > broadcast on the control channel for a particular device, or does it > say "Would anyone like to be 555-1212 today?" and listen for replies? I think it sends out a number first, ie, 555-1212, and if 555-1212 responds, some protocol takes over and an ESN match check is then done. If all checks out OK, the channel opens, and the phone starts ringing. This takes less than a second. (I was told by a tech guy at Cell One/Boston that BOTH the number and ESN are sent out initially, but perhaps I misunderstood what he meant by "initially"...) (I've been in systems where they did not SEEM to do an ESN/number check for incoming calls -- Cell One/ Stockton allowed me to RECEIVE calls, but not place them, since my cell number was not programmed into their switches. They may have still done as ESN check through their validation system, but you would think that if they could get an "OK" validation on my ESN/number, they could then use this info and assume that my number is a real cell number, and allow me to place calls, no? Weird ... this was in July of 1990 ... I'm sorry now that I didn't experiment further and put totally weird numbers into my phone, then call these numbers via the roam port, and see what happens ...!) > I'd appreciate it if one of you in-the-know people would give the > $0.05 lecture on how this all works, and/or point me toward a cellular > primer. Oh, sorry, that was only the two cent lecture! :) But that's because I doubt I'm an "in-the-know" person! I would suggest the "Red Radio Shack" book which has been mentioned here. A good, brief summary of how Cellular (they call it by its old name, "AMPS") works. If you are interested, I'll see if I can dig it up for an exact reference, but it is available at all Radio Shacks as is called *something* like "An Introduction to Telephone Electronics". Hope this helps, Doug (back from New Mexico where USWEST has no Follow Me Roaming! dreuben@eagle.wesleyan.edu // dreuben@wesleyan.bitnet [Moderator's Note: Actually, the way some cellular companies handle it now, like Cellular One - Chicago and Ameritech Mobile is if they / you want more than one phone to work on a a line, they exempt that number from any ESN checking at all. Example: a cell phone dealer has dozens or hundreds of phones in stock. He lets you test one out. He does not have dozens or hundreds of phone lines with the ESN of a phone in stock associated with each ... he has a special phone line for demo purposes which allows any cell phone to make calls, even one you bougvht from his competitor a year before that you programmed to the special demo phone number! Example: the cellular company customer service department has a few phones laying around they use in the office for tests. The cellular company technicians have phones they carry around all day. They don't want to have to be bothered carrying a certain phone to go with a certain line ... so the administrative phone lines at the cellular company itself as often as not are exempt from ESN checking. Then there are the temporary numbers assigned to roamers coming through town. When you issue a 'follow me' command, the cellular company assigns you a number and tells your home company to forward calls to that number. And those lines of necessity are not ESN-checkable either, so if you know what numbers your local cellular carrier uses for assignment to roamers, and you program your phone to that number, you will get incoming and outgoing calls just fine without the 'nuisance' of an ESN check. This is a gap the carriers should close down if they could figure out a way to do it. One thing they might try is to lock out calls (on demo and/or administrative phone numbers) not originating via the tower they would normally be expected to come on. The dealer will always be at the same location, after all, and his demo traffic would always be on the same tower. PAT]
Jack Decker <Jack.Decker@f8.n154.z1.fidonet.org> (06/20/91)
lairdb@crash.cts.com (Laird P. Broadfield) wrote: > Can you have two cellphones (I guess you can't call them "desk sets", > can you?) on the same number? I'm sure you could get ring-no-answer > and busy-forward from one to another, but I'm talking about for-real > both sets on one seven digit number. There is an advertisement that appears in _Nuts & Volts Magazine_ (_Nuts & Volts_ is sort of a "shopper" publication for amateur radio operators and electronic hobbyists, and if anyone is interested their address is P.O. Box 1111, Placentia, CA 92670, phone 1-800-783-4264 or FAX 714-632-3041) under the classification "Telephone - Fax" that reads as follows: ****BULL**** "You can't have two phones on the same phone number!!!" NOW YOU CAN. Call CELLUSOFT SYSTEMS for more information 9 AM - 3 PM EST. 616-399-6390. Disclaimer: I have no idea who this company is or what they're selling, but if anyone is interested enough to call and find out, I'd be interested to know what you come up with. From the area code and exchange, I'd guess that the company is in the Holland, Michigan area. Via D'Bridge 1:232/10 06/21 17:39 Jack Decker, via 1:120/183 (Great Lakes Internet<->Fidonet Gateway) Internet: Jack.Decker@f8.n154.z1.fidonet.org UUCP: ...!mailrus!umich!wsu-cs!royaljok!154!8!Jack.Decker
mohr@uunet.uu.net> (06/22/91)
In article <telecom11.467.2@eecs.nwu.edu>, lairdb@crash.cts.com (Laird P. Broadfield) writes: > Can you have two cellphones (I guess you can't call them "desk sets", > can you?) on the same number? I'm sure you could get ring-no-answer Each Cellular telephone made has a unique ESN. This ESN is programmed into the switch of the "home" operating system as a unique idenifier to the MID assigned to that phone. (MID = Mobile ID). Via one of several methods, this information is verified periodically by the service providing carrier.(not necessarily the "home" switch.) If a MID responds that does not have a matching ESN, then the ESN is denied (usually nation wide) regardless of MID. This is known as a Bandit mobile. > What happens if they're in the same cell? Nothing until they are called or try to make a call. If called, it becomes a race condition between the phones. If the correct phone answers first the call is completed, otherwise, the call is killed. Only the correct phone can make a call. The Bandit will be denied. (first and all subsequent.) ***discalimer**** This is true of the most simple cellular service offerings. Larger networks have a more agressive manner in which to validate subscribers. I truncated my description because of the complexity. For simplicity I have generalized the validation process description. > What happens if they both originate a call? > What happens if they both *answer* a call at the same time? Same holds true. Some service providers have services whereby you can have more than one phone to a number, but this is your usual hunt group scenario with each phone having a unique indentifier and the switch controlling the routing. (as it should be 8^) !) There are ways to beat this (as in all electronic validation schemes.) But this is costly and a BIG TIME federal offense. The most recent case involves a fraud scheme uncovered by the FBI and Secret Service. (Had us all running!) Wilson Mohr - Motorola CIG 1501 W. Shure Drive, IL27-2315 ..!uunet!motcid!mohr Arlington Heights, IL 60004-1497
lancelot@uunet.uu.net> (06/25/91)
I gave the CELLUSOFT SYSTEMS number a call this morning regarding
two cellular phones with the same ESN.
Talked with Mr. Hoser (sp?). For $300 + $35 s&h he'll send you a
device that allows you to program an ESN (specifically yours from
another phone that you own) into a Novatel phone. You provide the
Novatel phone (all models with #8320 base unit work according to Mr.
Hoser) and the ESN from your current phone. The procedure involves
removing the PROM from the Novatel phone, inserting the device in its
socket, entering a password and your current phone's ESN, and
reinstalling the PROM.
Two passwords are provided: one lets you program the ESN into the
Novatel phone the first time, the other lets you restore the old ESN
so you can sell the Novatel phone or have it repaired if needed.
He also has a dealer incentive program if you're interested.
He's sending me a brochure on the whole thing.
He indicated that he had gotten requests to do this for 'many'
cellular operators who have customers that want to have two phones
with a single number.