In order to perform its specialized function, a modem MUST be connected to a telephone line with dial tone.
Modems allow two computers literally to 'talk' back and forth to each other.
The sound is sent over a telephone line to another modem which turns the sound back to ones and zeros. Just like the signature throb of a Harley Davidson , the 'modem-squeal', once heard, is never forgotten. Using the baby speaker built into the unit, modem 'synching' becomes the ritual mating call of cyberspace. Once modems couple, the speaker usually gets turned off. This returns the pair to silence as they dutifully transmit and receive data across the phone line.