Plain Old Telephone Service

The Telephone System / Network

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@