International Telephone Dial Tone Signaling Reference 

[Copyright 1995,2000,2002,2004 Frank Durda IV, All Rights Reserved.
Mirroring of any material on this site in any form is expressly prohibited.
The official web site for this material is:  http://nemesis.lonestar.org
Contact this address for use clearances: clearance at nemesis.lonestar.org
Comments and queries to this address: web_reference at nemesis.lonestar.org]

The Dial Tone signal is used in Public Switched Telephone Networks to indicate that the telephone network switching equipment has recognized that a telephone has gone off-hook, and the switching equipment is prepared to receive the dialed digits or DTMF codes.

With the exception of one country (Italy), the dial tone signal is a constant signal and normally only stops when the first digit is dialed or the first DTMF code is received.

Japan also differs from all other countries, in that the volume of the dial tone is quite low, while the busy and ring-back signals are quite loud, where all other countries have the dial tone signal louder than the busy and ring-back signals.

Most switching systems will stop sending dial tone if no digits are dialed and no DTMF codes are sent in a reasonable amount of time. The typical time-out is ten seconds after no new activity.

Dial Tone Signal by Country
Country Frequency Second
Frequency
component
(if used)		 Period 1 On Period 1 Off Period 2 On Period 2 Off Amplitude
Belgium 450Hz   Continuous tone -12dBm
France 440Hz   Continuous tone -12dBm
Germany 425Hz   Continuous tone -12dBm
Israel 400Hz   Continuous tone -12dBm
Italy 425Hz   0.6sec 1.0sec 0.2sec 0.2sec -12dBm
Japan 400Hz   Continuous tone -20dBm
The Netherlands 150Hz 450Hz Continuous tone -12dBm
Norway 425Hz   Continuous tone -12dBm
Singapore 270Hz 320Hz Continuous tone -12dBm
South Korea 350Hz 440Hz Continuous tone -12dBm
Sweden 425Hz   Continuous tone -12dBm
Switzerland 425Hz   Continuous tone -12dBm
Taiwan 350Hz 440Hz Continuous tone -12dBm
United States 350Hz 440Hz Continuous tone -12dBm
United Kingdom 350Hz   Continuous tone -12dBm
This information is provided on an "AS IS" basis and has no warranty. Most countries have regulatory authorities who will have the latest specifications and compliance information.

Related Topics

Dual Tone Multi-Frequency (Touch-Tone®) Reference (HTML)
International Telephone Busy Signal Reference (HTML)
International Telephone Ring-Back Signaling Reference (HTML)
Information on dialing out-of-country numbers using a computer modem. (HTML)

Return to the Telecommunications Reference Index 

[Copyright 1995,2000,2002,2004 Frank Durda IV, All Rights Reserved.
Mirroring of any material on this site in any form is expressly prohibited.
The official web site for this material is:  http://nemesis.lonestar.org
Contact this address for use clearances: clearance at nemesis.lonestar.org
Comments and queries to this address: web_reference at nemesis.lonestar.org]

Visit the nemesis.lonestar.org home page and index

Valid HTML 4.01!