What is modem? Md. Saifur Rahman Modem is a device which transforms digital sign to analog sign (modulation process) and analog sign to digital sign (Demodulation process). Modem is the short form of Modulator and modulator.You may likeDo I need car insurance?What is car insurance?How could I get cheaper car insurance?What is auto insurance?Why Adulterant food is the barrier to sound health?What are the producers?What are food preservatives?What is food chain?What is tertiary consumer?