Internet Call Waiting is a technology that allows a telephone line

Telephone line

A telephone line or telephone circuit is a single-user circuit on a telephone communication system...

 to accept incoming calls while connected to an Internet dialup connection.

While online, a software application displays the Caller ID

Caller ID

Caller ID , also called calling line identification or calling number identification or Calling Line Identification Presentation , is a telephone service, available in analog and digital phone systems and most Voice over Internet Protocol applications, that transmits a caller's number to...

 of the incoming call, and allows the user to screen the incoming call. The user can then forward

Call forwarding

Call forwarding , in telephony, is a feature on some telephone networks allowing an incoming call to a called party to be redirected to a third party. For example, the third party may be a mobile telephone, voicemail box or other telephone number where the desired called party is situated. It was...

 the incoming call to another number, or disconnect from the internet and take the call immediately.

Most ICW software is currently fee based, but free software is also available.

One way to realize ICW is using SPIRITS (Service in the PSTN/IN Requesting Internet Service).