Call waiting
Encyclopedia
Call waiting in telephony
Telephony
In telecommunications, telephony encompasses the general use of equipment to provide communication over distances, specifically by connecting telephones to each other....

, is a feature on some telephone networks. If a calling party
Calling party
The calling party is a person who initiates a telephone call over the public switched telephone network, usually by dialing a telephone number....

 places a call to a called party
Called party
The called party is a person who answers a telephone call. The person who initiates a telephone call is the calling party....

 which is otherwise engaged, and the called party has the call waiting feature enabled, the called party is able to suspend the current telephone call
Telephone call
A telephone call is a connection over a telephone network between the calling party and the called party.-Information transmission:A telephone call may carry ordinary voice transmission using a telephone, data transmission when the calling party and called party are using modems, or facsimile...

 and switch to the new incoming call (typically, this is done by pushing the flash
Hook Flash
Hook flash or flash is a button on a telephone that simulates quickly hanging up then picking up again . This action can signal the telephone exchange to do something. A common use of hook flash is to switch to another incoming call with the call waiting service...

 button), and can then negotiate with the new or the current caller an appropriate time to ring back.

Call waiting, then, alleviates the need to have more than one line for voice communications. Note that since the waiting call creates an audible (for example, a 440 Hz beep every ten seconds in North America), call waiting can cause dial-up Internet access connections to terminate, unless the modem
Modem
A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...

 supports the most recent V.92 modem standard. For this reason, call waiting is often disabled on shared voice
Human voice
The human voice consists of sound made by a human being using the vocal folds for talking, singing, laughing, crying, screaming, etc. Its frequency ranges from about 60 to 7000 Hz. The human voice is specifically that part of human sound production in which the vocal folds are the primary...

/data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...

 telephone lines. In North America, the NANP uses *70 before a call to suspend call waiting for that call. A stuttered then regular dial tone
Dial tone
A dial tone is a telephony signal used to indicate that the telephone exchange is working, has recognized an off-hook, and is ready to accept a call. The tone stops when the first numeral is dialed...

 confirms the de-activation
Activation
Activation in chemical sciences generally refers to the process whereby something is prepared or excited for a subsequent reaction.- Chemistry :...

.

Type II Caller ID also works with call waiting.

History

Call waiting was introduced to North America in the early 1970s when the first generation of electronic switch machines built by Western Electric
Western Electric
Western Electric Company was an American electrical engineering company, the manufacturing arm of AT&T from 1881 to 1995. It was the scene of a number of technological innovations and also some seminal developments in industrial management...

,the number 1 ESS started to replace older mechanical equipment in the old Bell System
Bell System
The Bell System was the American Bell Telephone Company and then, subsequently, AT&T led system which provided telephone services to much of the United States and Canada from 1877 to 1984, at various times as a monopoly. In 1984, the company was broken up into separate companies, by a U.S...

 local telephone companies,. At first, some smaller municipalities had it only on a specific phone exchange (e.g., phone customers in Trenton
Trenton, Michigan
Trenton is a small city in Wayne County in the southeast portion of the U.S. state of Michigan. As of the 2010 census, the city population was 18,853...

, Michigan
Michigan
Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....

initially had to have a phone number starting with 671 to have call waiting due fact 671 was at that time the only exchange in that area served by one of the new ESS switches), but as demand for it became more widespread, it eventually became available on all phone exchanges as the older equipment was phased out.

External links

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