Call waiting

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Call waiting (or catch phone in Japan), in telephony, is a feature on some telephone networks. If a calling party places a call to a called 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 and switch to the new incoming call (typically, this is done by pushing the flash 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.

Star codes[edit]

For more details on this topic, see Vertical service code.

In North America, the NANP uses the *70 star code before a call to suspend call waiting for that call. A stuttered then regular dial tone confirms the de-activation.

On most European telephone networks, and GSM or UMTS mobile phones, call waiting is activated by dialing the following codes:

A voice announcement, tone or a message on your phone's screen will confirm the service status.

Call waiting in Europe uses an "R" (recall) button on the phone. This performs a similar function to a North American hook flash button but is much shorter duration, typically 80ms to 100ms, vs. 250ms in North America. In some networks, pressing R toggles between the calls, similar to North America. However, in most countries there are further options:

Type II Caller ID also works with call waiting.

Line sharing[edit]

Since the waiting call creates an audible signal (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 supports the most recent V.92 modem standard. For this reason, call waiting is often disabled on shared voice lines used for dial-up modem or fax purposes. However, Call Waiting has no impact on DSL connections.

History[edit]

Call waiting was introduced to North America in the early 1970s when the first generation of electronic switch machines built by Western Electric, Electronic Signaling System 1 started to replace older mechanical equipment in the old Bell System local telephone companies. At first, some smaller municipalities had it only on a specific phone exchange (e.g., phone customers in Trenton, Michigan initially had to have a phone number starting with 671 to have call waiting, since 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.

In Europe call waiting was also introduced in the 1970s with the introduction of the first digital switching systems such as the Ericsson AXE, Alcatel E10 and System 12. It was also available on some Ericsson crossbar exchanges, such as the ARE11 which, while electromechanical, was computerised. Other digital systems such as the UK's System X also supported the service. Switching systems developed in the 1980s such as the German Siemens/Bosch EWSD also had call waiting.

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