1. Ringback is typically used to refer to the audible ringing that is heard on the telephone line by the calling party after dialing and prior to the call being answered at the distant end. The ringback tone is different in various countries depending on the requirements for the ringback specification in those countries. For example, in the United States, the standard ringback signal is generated by summing a 440 Hz tone with a 480 Hz tone and applying these to the telephone line in a 2 second on and 4 second off cadence. The tone combination used in the United States produces a "ring... ring..." sound.

In recent years, a form of ringback has become popular on a global basis. This form of ringback is referred to as "personalized ringback." With personalized ringback, callers will hear an audio selection applied to the telephone line that has been previously determined by the called party. Audio selections can include music, messages, and special effects. Equipment is installed in the telephone network to enable replacement of the standard ringback tone with a personalized audio selection. The application of the personalized audio selections is accomplished with a subscriber account that can be modified through web, WAP, or IVR user interfaces.

Various companies supply personalized ringback equipment for wireless and landline telephone companies. The first company to launch a commercial system in the United States was Preferred Voice, Inc. (www.preferredvoice.com).

2. Ringback is a test used by many phone companies to quickly determine whether or not a new phoneline is working correctly and the phone number is routing properly. Look up test in Wiktionary, the free dictionary. ... TATA Engineering and Locomotive Company A telephone company (or telco) provides telecommunications services such as telephony and data communications. ... A telephone number is a sequence of decimal digits (0-9) that is used for identifying a destination telephone line in a telephone network. ... This article discusses routing in computer networks. ...

Typically it works by calling a "ringback number" and then hanging up. Often the ringback number plays a low frequency tone into the line to indicate that it's working, at which point the technician "flashes" the line (hangs up very briefly) to indicate they want a ringback. This makes the ringback play a higher tone to indicate it is working, and then the technician hangs up. The phone will then ring, answering only with a tone if picked up. A technician is generally someone in a technological field who has a relatively shallow understanding of the general technical principles of that technique compared to experts, but usually more than the average layperson. ... The word tone is used in several different fields with different meanings. ...

The tone is added so that telephone subscribers will not be able to easily use the ringback system as an "intercom," to call other extensions of their own phone line by simply initiating a ringback test and waiting for the phone to stop ringing (so as to know when the other person has answered).

New Zealand Telecom

In New Zealand, you just need to call the number, wait for the tone, then hang up.

137(Normal Tone)
136(Continuous Tone)

Telefónica de España landline system

In some areas of Spain, users connected to Telefónica de España landline system can obtain a ringback by dialling 020 and waiting for continuous tone. This article needs to be cleaned up to conform to a higher standard of quality. ...

Canada (Ontario) (Presumably Bell)

It used to be if you lived in Ontario, dialing the area-code 999 and then the remainder of the phone number would drop your line back to a dial-tone, but with a higher tone than normal. Then all one had to do was hang up, and quickly return to the line to hear a normal dial-tone again. Once the user hung up once more, a few seconds later the line would ring.

No longer useful due to the requirement of area-code use at all times in densely populated areas.

United Kingdom (British Telecom)

175 (Automated message rings back with the message 'Line Testing okay'.

Ringback Numbers

Toll Free

1-888-294-9681 - Ringback and ANAC An automatic number announcement circuit (ANAC) is a special telephone number that is meant to be used by phone company technicians and other telecommunications technicians to determine the phone number of a particular line. ...

FYI: 888-294-9681 has been disconnected as of 2006-01-11.