ANS:B - handshaking

The term used to describe the process of one computer establishing a connection with another computer or device. The handshake is often the steps of verifying the connection, the speed, or the authorization of a computer connection. An example of handshaking is when a modem connects to another Modem. The tones heard after the dialing are the handshake, indicating that the computers are greeting each other.

The squealing noise heard after the phone number is the Modem establishing a connection (handshaking). Once the connection is established, the Modem goes silent.