Is a modern an output device?

Answer 1

A "modem" is considered a transceiver. It receives data, and sends data. But it also converts signals in the sense that it can be seen as a DAC (digital to analog converter) and a ADC (analog to digital converter). Most dialup, DSL, and cable modems are examples of that - they plug into your computer and converts from-and-to your ISP the data you're receiving and sending. The signals you send from your computer are typically digital and the modem converts them into analog ones.