Hacker Chronicles 2 (Alt)/The_Hacker_Chronicles_Volume_II-CD2.iso/td2/td14_56.txt

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TELECOM Digest     Tue, 1 Feb 94 12:21:00 CST    Volume 14 : Issue 56

Inside This Issue:                         Editor: Patrick A. Townson

    Re: GTE is Annoyed With Me (John R. Levine)
    Re: GTE is Annoyed With Me (Thomas Lapp)
    Re: Sprint (Dvorak) Modem Offer (Joe Lynn)
    Re: Cutover Dates For New Area Codes (Carl Moore)
    Re: Wiretapping Problems (Gary Breuckman)
    Re: Telecommuting Centers in LA (Shuang Deng)
    Re: Broadcast Paging on Merlin 3070 System (Steve Cogorno)
    Re: Hello Direct Noise Filter Worth Getting? (Dale Worley)
    Re: Pager Software Wanted (Ron Stone)
    Re: How to Make a Sun Send Messages to a Pager or a GSM Phone (M. Cullen)
    Re: Small Cellular Phones With Data Capability (Lars Nohling)
    Re: Phone Line Simulator Wanted (Ben Burch)
    Re: Phone Number History (Steve Schlesinger)
    Re: EMI Filter for Phone Line (Michael Jacobs)
    Re: Data over Power Lines (Michael Jacobs)
    Re: Caller ID in Software ([e-mail])
    Re: DID Questions (Jay Hennigan)
    Re: DID Questions (Mike King)

TELECOM Digest is an electronic journal devoted mostly but not
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----------------------------------------------------------------------

Date: Mon, 31 Jan 94 19:44 EST
From: [e-mail] (John R Levine)
Subject: Re: GTE is Annoyed With Me
Organization: I.E.C.C., Cambridge, Mass.


> -- the local lightbulb manufacturer GTE

Actually, GTE sold Sylvania several years ago.  If you look at a
Sylvania box, you'll see the company name is now Sylvania/Osram.
Osram is an old Hungarian lightbulb company that GTE hooked up with as
the cold war ended; I don't know the financial details of the Sylvania
spinout.

Since GTE has also sold off their central office equipment business to
AT&T, this means that they have, in keeping with the latest in trendy
management theories, divested business units that distract them from
their primary mission: to provide the worst phone service in the known
universe.

Along sort of the same lines, I note that after buying Contel, they
quickly sold off a lot of the Contel properties.  In Vermont, for
example, Contel Cellular was sold to NYNEX, and Contel's wireline
properties were sold to Waitsfield Tel, a small but aggressive family
owned independent telco.  GTE's apparently sold off many of the Contel
California high desert properties as well.  Indeed, it looks like by
next year they'll have sold off all of Contel.  Given the relative
quality of service offered by GTE and the outfits they've been selling
to, the customers must be very relieved, but why did they buy it in
the first place?  Arbitrage?


Regards,

John Levine, [e-mail], [e-mail], [e-mail]

------------------------------

Date: Tue, 1 Feb 94 07:38:18 EST
From: Thomas Lapp <[e-mail]>
Subject: Re: GTE is Annoyed With Me


> Anyway, my printing of things published as internal communications at
> the lightbulb factory has gotten *some people* very, very upset and
> bothered, especially since they can't figure out who is sending me
> those bulletins.

I could see how this could happen.  I think it is just a matter of
timing.  Even though GTE is a regulated monopoly, they are still a
business with a public image as well as bottom line for shareholders.

I think that I would get a little miffed as well if I saw my internal
memos appear in a public forum within hours of their being created.
While I agree that the media pipe from them might not have all the
details that you get, it may also be true that the media office isn't
getting fed that info either.  So, if you didn't get detail, it might
not be intentional on their part.

It might be curious to see what information you could get two to four
weeks after the event.  Journals like IEEE Spectrum seem to get access
to a lot of info when doing stories on things like failure of the NYC
power grid.  Who knows, maybe the media office could even help you get
post-event internal information.


internet     mvac23![e-mail]  or  [e-mail] (home)
             [e-mail] (work)
OSI          C=US/A=MCI/S=LAPP/D=ID=4398613
uucp         {ucbvax,mcvax,uunet}!udel!mvac23!thomas
Location     Newark, DE, USA

------------------------------

From: [e-mail] (Joe Lynn)
Subject: Re: Sprint (Dvorak) Modem Offer
Date: 01 Feb 1994 10:30:40 -0600
Organization: Macro Computer Solutions, Inc.


[e-mail] writes:

> I called Sprint in September to sign up for the offer (and was also
> assured it was a 9600 baud external modem).  My line was switched to
> Sprint.  I never received the modem, and every time I called I was
> told something different.  For a few months, I was told the modem

For what it's worth, I signed up for the Dvorak offer in mid-September
and completely forgot about the modem (too many things going on, I
suppose): it showed up two weeks ago.

It's a 9600 baud fax/2400 baud data internal modem.  It's not
elaborate, and I haven't taken the time to install it, but it's here,
at least.

Now MCI is offering me free AAdvantage miles if I switch over to them.
We'll see.. :-)


[e-mail]


[TELECOM Digest Editor's Note: AT&T's thing now is frequent flyer miles
on several participating airlines also.   PAT]

------------------------------

Date: Tue, 01 Feb 94 13:31:59 EST
From: Carl Moore <[e-mail]>
Subject: Re: Cutover Dates For New Area Codes


> I am aware that there are at present three new area codes scheduled
> for 1995: 334 in Alabama, 260 in Arizona, and 360 in Washington.

That is 520 (to be formed by splitting 602) in Arizona, and the only
information I have for its startup so far is March 1995.

Please refer to the history file in the archives or to a slightly-later
version available directly from me (I do mail it out on request).
How do you arrive at the 8 Jan 1995 permissive date for 334 in
Alabama?  (I have 15 Jan 1995, one week later.)

------------------------------

From: [e-mail] (Gary Breuckman)
Subject: Re: Wiretapping Problems
Date: Tue, 01 Feb 1994 02:53:59 GMT


In article <[e-mail]> [e-mail]
(Disini SW, Emmanuel Disini,CST) writes:

> I am a bit concerned that my phone could be tapped (I am located in
> Manila, where wire-tapping laws are not enforced all that well). Is
> there some way I can tell that my phone has been tapped?  My guess is
> that there should be some drop in ambient voltage (on one of the RJ-11
> leads- TIP? RING?) if a tap is placed on your phone. However if the
> wiretap is already in place and I look at the voltage after the tap
> has been installed, I would not be able to detect it, right?  Pls cc
> your responses to [e-mail], as I don't get this
> newsgroup.

If you are concerned about someone bridging your line and using it to
make calls, that should be easy to detect.  If you are worried about
someone listening in, that's real hard to protect against since many
high-impedance taps will not cause any voltage drop on the line.
Equipment does exist to measure such things, but you would normally
want to do that from the office end so the cable could be disconnected
from their equipment.  There is also a device (TDR, time-domain-
reflectometer) that will bounce a signal down the line and give you a
visual indication of bridge taps or irregularities in impedance along
the circuit.  You can usually see any splice or terminal box.


[e-mail]

------------------------------

From: [e-mail] (Shuang Deng)
Subject: Re: Telecommuting Centers in LA
Organization: GTE Laboratories, Waltham, MA
Date: Tue, 01 Feb 1994 18:11:16 GMT


I remember seeing a news release somewhere mentioning that GTE set up
a telecommuting center for its employees in LA area.  I seem to recall
that it's a joint effort between GTE, PacTel and some other companies
and government agencies.  That's all I can recall now.

I agree there are business opportunities to provide telecommuting
services now in that area.  By the time roads are back to the normal
(say in a year), the users will probably keep using the service, for
they have realized the benifits of telecommuting and worked out the
solutions to management and other social issues.


Shuang Deng            |  Email:   [e-mail]
GTE Laboratories       |     or     [e-mail]
40 Sylvan Road         |  Phone: [phone]
Waltham, MA 02254, USA |  Fax  : [phone]

------------------------------

From: [e-mail] (Steve Cogorno)
Subject: Re: Broadcast Paging on Merlin 3070 System
Date: Tue, 01 Feb 1994 13:22:58 PST


Said by: Brian Nunes

> Does anyone know how to simultaneously page all stations using a
> Merlin 3070 system?  One of the people in my office did it by mistake
> once but couldn't remember what she did.  When I called AT&T, they
> told me it couldn't be done, but I know it's possible.  Maybe it's
> undocumented?  Does anyone know?

On a Merlin Plus the Page codes are 70, 71 and 72.  (70 being all,
71-group 1, 72 group 2)

I know that the control codes are somtimes different, but I would
assume that these might work because 3070s have a max of 70 extensions.


Steve  [e-mail]
#608 Merrill * 200 McLaughlin Drive * Santa Cruz, CA 95064-1015

------------------------------

From: [e-mail] (Dale Worley)
Subject: Re: Hello Direct Noise Filter Worth Getting?
Date: 1 Feb 1994 11:58:53 GMT
Organization: Village of Cambridge, Public-Access Internet


Michael Rosen ([e-mail]) wrote:

> I'm looking at the EMI noise filter in the Hello Direct catalog.  I
> currently only have a surge suppressor from Rent-A-Shack on my phone
> line.  How do I know if I truly need a noise filter?  Could it make
> improvements even though I currently don't notice many problems?

I found an EMI filter to be useful.  It turns out that my phone line
was picking up a local radio station.  This didn't cause a problem on
voice calls, presumably because my phone and the CO are insensitive to
RF.  But when my modem went off-hook, it proceeded to rectify the RF
into audio, and put it back on the line!  So while the modem was
dialing and attempting to connect, I could listen to the radio for
free!  After a number of calls, I managed to hear the callsign.
Putting in an EMI filter fixed the problem.


Dale

------------------------------

From: [e-mail] (Ron Stone)
Subject: Re: Pager Software Wanted
Organization: Carleton University
Date: Tue, 1 Feb 1994 07:29:48 -0500


In <[e-mail]> Sean Slattery <Slattery+acyberspace%
[e-mail]> writes:

> I am considering getting a pager to alert me of problems on my
> network, i.e. server down, WAN down etc.  The software offered by the
> major paging company's seems geared to use by a human and doesn't seem
> to have a machine interface.

> Does anyone know of a software package designed to monitor Netware or
> Unix (perferably both) networks and send alpha messages to a pager if
> certain events occur (or don't occur)?  Alternatively a package with
> an interface to which I could add my own scripts/batch files?

The company I work for (Caravelle Networks Corp.) has a product for
the PC called NetWORKS/PC, which does the type of thing you are asking
about. It is designed as a multi protocol LAN Management tool with the
ability to inform the administrator of problems in a variety of local
or remote ways, including paging. You can set calanders of the times
you will or will not be paged, so that for instance, a page will not
wake you up at 3am on a Saturday if something goes down, but will wake
you at 6am on a Monday. NetWORKS/PC also supports detailed statistics
gathering about Netware servers and SNMP devices. Usings these stats,
you can decide at what threshold you wish to be alerted about a given
parameter.

It is also available for the Mac.

Our phone number is 1-800-363-5292.

PS: I am sorry if this sounds to anyone reading like a commercial
plug. I am replying because it sounds as though this product is the
type of software you were asking about, and from what I know, its the
only software with this combination of multi-protocol support and
remote notifications.

Ron Stone    [e-mail]


[TELECOM Digest Editor's Note: Ah, don't worry about commercializing
'the net'. I do it all the time. Take it from me, Patrick "Make Money
Fast!" Townson, before I started commercializing the net with my products,
I was riding around in an old 1981 Chevy Cavalier. Well, within a month
of sending out my first mass-mailing for the Orange Card, my car had
been reposessed for late payments by the used car dealer who had sold it
to me, and I started paying my phone bills three months late instead of
two months late like I always had to do before. Like Ron Doaks or Joe
Blokes or whatever his name is who posts his messages with evangelistic
fervor in news.groups (it used to be every couple months, now lately
there is a new one every few days), I am really starting to live in the
style to which I am accustomed.  :)   PAT]

------------------------------

From: [e-mail] (Martin Cullen)
Subject: Re: How to Make a Sun Send Messages to a Pager or a GSM Telephone
Organization: Devteq Ltd
Date: Tue, 1 Feb 1994 13:00:32 GMT


[e-mail] (Jurgen Debedts) writes:

> I'm looking for something quite special:

> We would want to have our Sun, (which is running critical
> applications), dial-out to a semascript pager to tell the sysadmin
> something is wrong. Typically, we have some sort of contool, which
> send a certain fixed message for a certain error-situation. This
> messages would then in fact be send to a modem that dials up a
> semascript pager, and passes on the error.

> In our dreams we would like to go even further, and have the Sun dial
> up a GSM telephone, and have the Sun speak to the sysadmin saying that
> there is a problem. (pre-recorded fixed messages). In this case, we
> thought of have a modem that directly dials up a GSM mobile telphone.
> But there are some problems to be solve with this: for example, a GSM
> will not give a Carrier Detect, only a connect signal. Anybody delt
> with this kind of problems before?

> Does anybody out there know of software that does one of these two
> things, or does anybody have some tips, or thoughts he or she would
> like to share with me?  (Like which modems could we use, etc)
> The software may be commercial or public domain.

There are a couple of things you could do but it will all be dependant
on what facilities are supplied by you're network operator.

You cannot use a modem as what you are describing above is a voice
call, not a data call, if tried to do this then the network would
treat the voice as modem tonals everything would fall apart. What you
need to do is to get the SUN to establish a voice call to mobile,
possibly using the modem to establish the connection but when this is
done, take the modem out of the loop and send the voice. I don't know
how easy / possible this is but if you manage it then let me know.

Another thing you could use is the Short message capability of the
mobile phone. I would think that you network operator should offer
dial in access to their short message center then you could send short
messages in a similar way that you are currently using the pager.

Hope this helps.


Martin Cullen

------------------------------

Date: Mon, 31 Jan 94 13:31 EST
From: Lars Nohling <[e-mail]>
Subject: Re: Small Cellular Phones With Data Capability


The only direct connection between phone and modem that I know is
shipping is the Nokia Portable phone + AT&T's Keep in Touch PCMCIA
modem.

Motorola has announced a direct connect PCMCIA modem for the flip
phone but it has not started shipping yet. You can buy the "Cellular
Data Adapter" from Motorola that will provide an RJ11 jack for the
flip phones. It works fine but an extra black box + cables is a
hassle.

Megahertz has announced a PCMCIA modem the will direct connect to NEC
and several other phones.

In the next six months the market should be full of options.

If you can't find these things in you area I work for a reseller who
has a group the specializes in selling "Mobile Office" solutions,
laptops, modems, cell phones and pagers.


Lars Nohling  Business Systems Solutions, inc.   [e-mail]

------------------------------

From: Ben Burch <[e-mail]>
Subject: Re: Phone Line Simulator Wanted
Organization: Motorola, Inc
Date: Mon, 31 Jan 1994 20:39:30 GMT


In article <[e-mail]> ssatchell on BIX, ssatchell@
BIX.com writes:

> The cheapest I'm aware of is the PTT 5101, if you can find one
> used.  They are located in Huntsville, AL and you can call (205)
> 971-8001 for more information.

I've used both the 5101 and 5102 machines.  They work quite well, and
are very flexible.


Ben Burch   Motorola Wireless Data Group
[e-mail]

------------------------------

Date: Mon, 31 Jan 94 16:47:30 PST
From: Steve Schlesinger <[e-mail]>
Subject: Re: Phone Number History
Organization: NCR (Torrey Pines Development Center)


> [TELECOM Digest Editor's Note: Well, I gave a hasty rendition of the
> history. We went from 3L/4D to 2L/5D about 1950 or so; then about 1960
> we began seeing 7D in the phone book and as the only way things were
> being assigned. We had a mix of 2L/5D and 7D in the phone book from
> about 1960 through the middle 1970's at which point the few remaining
> (on paper only, in the directory) 2L/5D listings were expressed only as
> 7D.   PAT]

Before 3L/4D wasn't there 2L/4D?


Steve Schlesinger, NCR/Decision Enabling Systems Division          619-485-3528
16550 West Bernardo Dr. San Diego, CA 92127               ucsd.edu!sv001!steves
NCR VoicePlus 440-3528                     [e-mail]


[TELECOM Digest Editor's Note: Not that I know of. Before name/number
combinations (which existed almost from the beginning in big cities)
there were just numbers. In small towns, one to four digit numbers were
common and that was it. If a town had only one exchange, or switchboard,
its name was usually the name of the town where it was located, and
reciting it as part of the number was redundant. When things expanded
to include names, some towns got to keep their (town) name as the phone
exchange name; i.e. Atlantic City, NJ still has the exchange name
ATlantic City, although 285-xxxx is the way it is expressed now. Where
conflicts occurred, they made up other names for conflicting exchanges.
When a community went from manual service to dial service, in order to
fill out the dialing string to seven digits zeros were prepended to the
shorter numbers. For example, the Walgreen's Drugstore in Whiting, IN
had the old number (Whiting) 72 for upteen years. With the conversion
to dial, WHIting was unavailable since at that time one could dial a
Chicago number (WHItehall-xxxx) without area codes, so Whiting (which
cut to dial about 1962 after 'all number dialing' was already the
rule) got '659'. The drugstore went overnight from 'Whiting 72' (or
just plain '72' when asking the operator for the number) to the
new format: 659-0072.

The Amoco Oil Refinery which makes up about ninety percent of the
physical space in Whiting oddly enough had a dial PBX system in place
for a few years before Whiting went from manual to dial service. When
you dialed '9' from the PBX instead of getting a new dialtone you
simply sat there a couple seconds and the 'number please?' lady came
on the line. Their switchboard number was (Whiting) 2111 and it of
course became 659-2111, although under the old system no one actually
asked the operator for 2111, they merely would say 'Refinery' or
'Standard Oil' (as it was known in those days), and the operator would
immediatly plug them into one of a dozen or so lines going into the
company PBX. Hunt groups in those days consisted of the operator
looking up at the several jacks all going to the same company and
selecting one which did not already have a plug in it.  PAT]

------------------------------

Date: Tue, 01 Feb 94 00:02:41 EDT
From: Michael Jacobs <[e-mail]>
Subject: Re: EMI Filter for Phone Line


In TD V14 #49, the question was asked about benefits of an EMI filter
and relevance to being unable to make dial-up connections at speeds
greater than 9.6 kbps.

1) An EMI (ElectroMagnetic Interference) filter is designed to reduce
the effects of induced Radio Frequency energy onto a telephone line.
If you are not having RFI problems (ie-you do not hear an AM radio
station or Ham or CB operator on the line), it will be a waste of
money, as it will not reduce metallic or impulse noise.

2) Noise on the line is not the only determinant of data transmission
speed.  Depending on the circuit makeup (loaded or non-loaded, pair
gain or copper, and length/number of bridge taps), and overall
distance from the CO, a voice-grade telephone line may not be able to
carry speeds over 1200 baud.  Most telcos do not guarrantee that you
can send data at all!  A voice line is just that, for voice.
Conditioned dial-up data circuits are available from most telephone
companies; there may or may not be an additional charge to improve
the line transmission to accommodate your required data rate.


Michael W. Jacobs <[e-mail]>
Service Technician Bell Atlantic-Pennsylvania

------------------------------

Date: Tue, 01 Feb 94 00:29:57 EDT
From: Michael Jacobs <[e-mail]>
Subject: Re: Data over Power Lines


I have become concerned lately by the proliferation of technical
devices of dubious efficacy which propose complicated alternative
solutions to simple problems.  In this case, I refer to those devices
which allow the telephone user in need of an extension telephone jack
to use a simple device which plugs into the house electrical wiringand
then gives you a jack at any outlet.

The prices I have seen for these devices are substantially higher than
the cost for having a permanent jack installed by the telephone
company (or other vendor).  For $150 for the base transmitter and $60
for the remote unit, or a total of $210 you can have a professional
Bell Atlantic technician (like me!) give you 2 1/2 hours of premise
work.  For comparison, the time it takes an experienced technician to
install a jack can be as short as fifteen minutes, and probably rarely
exceeds an hour.  For situations where one does not expect to
frequently relocate a jack, a permanent installation is, IMHO, better
than these devices.

Also, as a technician working on telephone lines daily, I have some
serious reservations about the safety of these devices and the
potential that in the event of a component failure they could backfeed
house current onto the telephone line, resulting in fire, injury, or
worse to both the homeowner and telephone workmen.

Other devices of questionable economic value include those devices
which interface fax machines and modems to electronic key telephone
equipment.  Customers should consider the cost of these devices, not
only installation, but operating inconveniences and maintenance also
when making a decision.  It is usually much simpler and more efficient
to install a dedicated line and jack for these devices, as it
eliminates the frustration of conflicting uses of a line, particularly
on incoming calls.


Michael W. Jacobs <[e-mail]>
Service Technician Bell Atlantic-Pennsylvania

------------------------------

From: [e-mail]
Subject: Re: Caller ID in Software
Organization: KAIWAN Internet Access Service
Date: Mon, 31 Jan 1994 23:54:15 GMT


In article <[e-mail]>, Chris Farrar wrote:

> [e-mail] said something along the lines of the following:

>> is a good question.  I also have such a modem, and I've been looking
>> for a utility like this ever since I got Caller ID (New England
>> Telephone calls it PhoneSmart).  It would be even better if it had an
>> automatic logging capability.  Anyone seen something like this?

> ICON CS Canada Inc. sells a hardware board for a PC that will capture
> CLID info, maintain a log, and even route the call to a specific port
> (port 1, 2, or 3, or NUL) so you can decide who you want connecting.

> Write [e-mail] for more info

Try ZyXEL modems with their free ZFAX 3.02eb(PC only) program.  You
can get ZFAX 3.01 free from anonymous FTP kaiwan.com. and test run it,
but you need a ZyXEL modem to make it work.

ZFAX Specifications:

FAX:
      Send faxes
      View fax files
      Print fax files
      Polling fax from remote fax
      Ability to receive faxes manually
      Convert document files to TIFF, PCX, FAX, or PRN
      Capture printouts from other applications and send them out as faxes
Voice:
      Send voice files to a remote telephone number
      Record voices from a telephone set or external microphone
      Play voice files to a telephone set, internal speaker or SoundBlaster
      Convert voice format to AD2 (2-ADPCM), AD3 (3-ADPCM), or VOC (Sound-
      Blaster)
Data:
      External terminal program
      ZFAX internal terminal program
      Send data files to a remote modem using ZMODEM protocol
      Receive data files from a remote modem using ZMODEM protocol
Voice Mail:
      Up to 1000 mail boxes
      Greeting message management
      FaxBack document management, 10 files
      Voice announcement management, 10 files
      Phone transfer for small PBX
      Page operator
Tx/Rx Log Reports:
      Fax in
      Fax out
      Voice messages
      Outgoing FaxBack documents
Utilities:
      Manual answer
      Dial any remote fax number
      Execute external editor program of your choice
      Phone book management (grouping is also supported)
      Schedule management: voice, fax and data calls (uploading files)
Setup Configurations:
      General hardware
      RS-232 and modem
      Fax configuration
      Distinctive ring feature
      Voice mail configuration
      Cover page configuration
      Printer capture configuration
      ZFAX and related programs' paths

Caller ID and Distinctive Ring:
      Logs Caller ID information and displays it on the screen
      Allows different Actions to be taken for different Rings

      Supported actions:
            1. Ignore
            2. Fax only
            3. Voice Mail System
            4. Data handshake and file transfer
            5. Data handshake and shell to external program
            6. Detect ringing and shell to external program


[e-mail],Anonymous FTP,Telnet kaiwan.com(192.215.30.2)FAX#[phone]
Data Lines# [phone],452-9166, [phone], [phone],756-0180
ZyXEL U-1496E 16.8K: $279.00, U-1496E+ 19.2K: $389.00 Voice/FAX/Data Modems

------------------------------

From: [e-mail] (Jay Hennigan)
Subject: Re: DID Questions
Date: 31 Jan 1994 20:13:56 -0800
Organization: Regional Access Information Network (RAIN)


In article <[e-mail]> Thomas Tengdin <teto@mbari.
org> writes:

> Can anyone tell me how DID lines pass the number down the trunk?

The answer is, "It depends."

DID signaling options are specified when service is ordered, and vary
by the customer and telco.  Generally, the customer provides battery
and ground on a two-wire DID trunk.  When a call comes in, the CO seizes
the trunk by drawing loop current.  At this point, there are three
choices: Immediate, delay dial, and wink.  Immediate means that the CO
will transmit the number immediately.  Immediate trunks virtually
always use dial pulse signalling.  It is assumed that the customer's
equipment is always ready to receive the information.  DTMF is not
used for immediate signalling as most PBX systems dynamically assign
DTMF receivers, and one may not be "immediately" available.

Delay dial means that after a preset interval the CO will transmit the
number.  Dial pulse signalling is the method of choice here also.  10
or 20 PPS can be used, as specified by the customer when the order is
placed, if available from the telco.  Wink signalling is most commonly
used, especially with DTMF.  When the CO seizes the trunk, the
customer will detect the loop current and breifly interrupt battery or
reverse polarity.  The CO sends the information at the end of the
"wink".  So, the wink acts as a "ready to receive" signal from the
customer to the CO.  The CO then outputs the digits either in DTMF or
pulse.  An option on some PBX systems is to supply dial tone when
ready to receive, but I'm not aware if "dial tone" is an option
supported by any local exchange carriers.

Another important factor in DID trunk usage is the return of answer
supervision from the customer to the CO.  When the called party
answers, the PBX will reverse the polarity on the loop.  This reversal
is used by the CO to start timing the call for billing purposes.  All
of the above examples are for simple analog 2-wire DID circuits.
T-carrier systems still typically use DTMF or pulse transmission, but
the A and B signalling bits are used for supervision.

The number of digits sent and any translations from what is dialed to
what is sent are also specified on the order and subject to agreement
by the serving telco.


Jay Hennigan    [e-mail]  Santa Barbara CA

------------------------------

From: [e-mail] (Mike King)
Subject: Re: DID Questions
Date: Tue, 1 Feb 1994 09:23:17 PST


In TELECOM Digest, V14 #53, Thomas Tengdin <[e-mail]> asks

> Can anyone tell me how DID lines pass the number down the trunk?

Sure.  There is a set of trunks from the CO to the PBX.  When a call
arrives at the CO that is in the group of numbers "belonging" to the
PBX, the CO will select one of the DID trunks and, in effect, take the
trunk off-hook.  The PBX provides battery to the trunk pair in the
same manner the CO provides battery to a normal two-way trunk.

When the PBX recognizes the CO has "seized" the trunk, it will signal
to the CO to send the identification of the dialed number.  The PBX
does this by momentarily removing battery current; a "wink" condition.
When the CO detects the wink, it will then begin pulsing the dialed
extension to the PBX.  This number may be two to five digits.  The PBX
is then responsible for completing the call to the extension, and
returning ring signal or busy.  If the dialed number does not exist,
the PBX is required to provide some sort of intercept.  Also, the PBX
will return supervision to the CO when the call is answered.

Newer PBXes can receive the extension indication via DTMF.  This is
known as DID-II.


Mike King    [e-mail]

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End of TELECOM Digest V14 #56
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