The Telephone System

aka POTS (Plain Old Telephone Service)

Country codes

Phone Number Directories

Location Data From Phone Number

http://www.AreaDecoder.com Country and Area Codes. Forward and reverse. Partial matches ok. Nice job. See also

• http://www.nanpa.com/ North American Numbering Plan Administration
• http://www.nanpa.com/number_resource_info/adm_state.html area code to state list.
• http://www.nanpa.com/number_resource_info/co_code_assignments1.html Area code and exchange to CO list. The "rate center" field more or less tells you what city the phone number is in.
• http://www.wtng.info World Telephone Numbering Guide

Phone line interfaceing

Voice Mail Systems

D.C. Line Voltage (Talk Battery) - 48v with receiver on-hook, red wire (ring) negative, 5v for off-hook (with 50-1000 ohm d.c. load on line).

Tip and ring get their name from the construction of an operator's plug-board plug -- tip was the tip, and ring was the ring below the tip. The positive voltage (ground) was put on the tip line, because that was the part of the plug that the operator had the least chance of touching. Negative battery supplies (with respect to ground) have always been used with phone systems, so that leakage currents to ground caused by moisture do not electroplate away the copper in the wires.

Call Progress Tones in the US (from many sources includeing Telecom Digest, Dan Michaels and others as listed)

• Ring: 20-90 vp-p, at 20-40 hz
• Dial tone: 350+440Hz Continuous
• DTMF Tones - 1 high-band plus 1 low-band sinewave at frequencies shown in DTMF Table, at max transmission level of 0 dBm averaged over 3 sec (approx 24.5v RMS), for minimum of 50 msec duration and 45 msec interdigit time.
• Busy:
  • Busy tone: 480+620Hz 0.5s ON 0.5s OFF
  • Reorder: 480+620Hz 0.25s ON 0.25s OFF
• Ring back tone:
  • Most common: 440+480Hz 2.0s ON 4.0s OFF (the initial ring on some telephone exchanges may range from 0.5s ON to2.0s ON)
  • Some PBXs: same frequency, but cadence varies from (1.0s to 1.5s ON and 2.0s OFF to 3.5s OFF)
  • Mitel PBXs (When calling from outside) same frequency, but 0.5 ON 0.5 OFF 0.5 ON 1.5s off (burr burr burr burr....)
  • (Internal calls) 1.0s ON 3.0s OFF
• SIT  (Special Information Tones) tones: the triple tone that you get when you dial a number that doesn't exist (3 tones, each higher in pitch than the last) Used by CDA (Call Disposition Analyzers) to differentiate between human voices and recorded announcements and categorize their type. Most CDA's merely look for three sequential tones occurring in less than 3 seconds using a bandpass filter centered around 600 Hz.
  
  Loren D. Cahlander of Ensodex, Inc. 4105 North Lexington Ave, Suite 150, Arden Hills, MN 55129

  From the documentation that I have, there are four different sequencesof tones:

  			First Tone	Second Tone	Third Tone
  Tone	Tone		freq   length	freq   length	freq   length
  Name	Description	(Hz)   (10 ms)	(Hz)   (10 ms)	(Hz)   (10 ms)
  ======================================================================
   NC	No Circuit	985.2  38.0	1428.5  38.0	1776.7  38.0	Found
   IC	Operator	913.8  27.4	1370.6  27.4	1776.7  38.0	Intercept
   VC	Vacant Circuit	985.2  38.0	1370.6  27.4	1776.7  38.0
   RO	ReOrder		913.8  27.4	1428.5  38.0	1776.7  38.0
  

  Macy Hallock of F M Systems, Inc. 150 Highland Dr. Medina, OH 44256 says:

  Period  Frequency    Designation
   SSL      LLL        IC - Intercept - Vacant No. or AIS or etc.
   LLL      LLL        NC - No Circuit (Inter-LATA carrier)
   LSL      HLL        VC - Vacant Code
   SLL      HLL        RO - Reorder Announcement (Inter-LATA Carrier)
   LSS      LHL        #1 - Add'l Reserved Code
   SLL      LHL        RO - Reorder Announcement
   SSL      HHL        #2 - Add'l Reserved Code
   LLL      LLL        NC - No Circuit, Emergency or Trunk Blockage
  Where: Period-Duration: S=Short 274 msec   L=Long 380 msec
         Frequency: L=Low  913.8 hz  1370.6 hz  1776.7 hz
                    H=High 985.2 hz  1428.5 hz
  

  This information taken from a central office recorder/announcer installation manual ca. 1983. I believe SIT's are specified by Bellcore and/orr CCITT. I have heard SIT's used on international calls to several countries.

  Teltone (http://www.teltone.com) makes a detector chip; part number M-984-02.
  

• Receiver Off-Hook Tone: (when someone forgets to hang up the phone) quad 1400, 2060, 2450, and 2600 hz tones, pulsed at a 5 hz rate.
• Speech Signals: 200 - 3400 hz, bandlimited
• Answering machines
  • techniques for "call progress detection are readily available by looking at sample patents:

    U.S. Pat. 5,724,420

    Automatic Call Distribution with Answer Machine Detection

    U.S. Pat. 5,430,792

    Automated Telephone Calling System

    U.S. Pat. 5,371,787

    Machine Answer Detection

The GSM specification (mostly) requires phone numbers in the format

+XXX-LLL-YYYYYYYYY...

+ = International access
XXX = country code
LLL = local area code
yyy   = number

This string cannot exceed 12 digits

Speech@ Fax@ Pagers@ Modems@ DTMF@ Cellular@

See also:

• http://www.howtocallabroad.com
• newmanrfSPAM at ~NOSPAM~embedworx.com refers to

• http://embedworx.com/articles/index.html The phoneswitch.com url is outdated. The correct URL is here: http://embedworx.com/articles/index.html I'm the author of the original Personal PBX article. Thank you.

  James Newton replies: Thanks for the update!+

  +

• webmasterSPAM at ~NOSPAM~quentinsagerconsulting.com refers to " http://www.quentinsagerconsulting.com/phonecodes.htm Detailed North American NPA NXX lookup." +
• http://telecom-digest.org
• http://www.cisco.com/warp/public/788/VoX/net_signal_control.html Voice Network Signaling and Control
• http://www.phoneswitch.com . There is a 8051 CPU in the schematics of the Personal PBX.
• http://www.tinaja.com/glib/muse127.pdf Don Lancaster's Tech Musings #127 on a transformerless DAA from Silicon Laboratories
• http://www.ccc.de/Library/HPA/Boxing/Boxing.html box hacking
• http://www.ee.washington.edu/eeca/text/callerid/spec.html
• http://www.hut.fi/Misc/Electronics/circuits/teleinterface.html
• http://www.geocities.com/SiliconValley/Station/6369/links/electr/telephone.html
• http://www.shout.net/~wildixon/index.html TELECOMMUNICATIONS TIDBITS compiled by Wil Dixon
• http://www.pacific.net/~brooke/phones.html
• Caller ID
  • http://www.tmworld.com/articles/98articles/caller_id_0998.htm
  • ftp://www.gernsback.com/pub/EN/cid.zip
  • ftp://www.gernsback.com/pub/EN/cid2.zip
  • Specified by TA-NWT-000030 obtained through Bellcore Customer Services, 60 New England Ave. Piscataway, NJ 08854-4196 908-699-5800
  • http://www.ainslie.org.uk/callerid/cli_faq.htm
  • http://www.exar.com/products/xr2206.html
  • http://www.exar.com/products/xr2211.html
• pbx's
  • http://www.playground.net/~mwandel/pbx.html
• Pay Phones
  • http://www.payphone-directory.org/phones.html
• manufacturers
  • Teltone has a line of telephony ICs including call progress tone detectors
  • Mitel has a line of pbx ICs. Their SLICs, COICs and analog switch matrix devices allow you to easily build a PBX with very few additional components
• Staying off the telemarketers phone lists:
  • http://www.scn.org/~bk269/data.html
  • Richard Anthony asks:

    I am looking for a gadget similar to what my friend, Vinny, has. I call it their 'Do Not Disturb gadget'. They bought it at least 10 years ago and I have never seen its like. It sits there on the telephone line, like an answering machine. But when you call his number it answers, usually on the first or second ring. It does not say anything (but I am OK if the one I buy says a message), but unless you enter the special three-digit code (I am cool with more or less digits) your call is going nowhere. When you enter the code, then it 'passes' the call, -- that is, other telephone(s) on the line ring -- and if they are at home one of them will answer. There is no audible ring anywhere in the house until then.

    James Newton reffers to : "http://www.hometownvariety.com/wholesalestuff/digcalfil.html".

Questions:

• johnksi at yahoo,c0m asks:

• Your link to http://www.nanpa.com/number_resource_info/co_code_assignments1.html
  (such as from http://www.sxlist.com/techref/pots.htm ) is dead.
  Is there a new/different NANPA link?
  
  -John

  James Newton replies: Looks like they automated it. Check out
  http://www.nanpa.com/nas/public/assigned_code_query_step1.do?method=resetCodeQueryModel James Newton replies: John says it is at http://www.nationalnanpa.com/reports/reports_cocodes_assign.html+

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