Call waiting

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.

Since the waiting call uses a zip tone (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.

Call waiting deluxe is the Bellcore (now Telcordia Technologies) term for Type II caller ID with Disposition Options.

[1] This CLASS-based POTS-telephone calling feature works by combining the services of call waiting with caller ID but also introduces an "options" feature that, in conjunction with certain screen-based telephones, or other capable equipment, gives a telephone user the option to: