Analog 

Here is a picture of an internal analog modem. This modem is an expansion board for the ISA slot.

Using this theory the analog modem was born. The modem converts the digital signals into analog signals using variation in tones to distinguish the 1s and 0s. When the message is sent, the signal is converted into analog data or modulation, then, it is received and demodulated into a digital signal again. That is the simple theory behind analog modems.

The only drawback in analog modems is the threshold of speed allowed in the phone lines. Phone lines limit the speed of modems to 56KBps. Also, with increase of distance and noise, analog modems sometimes severely decrease in performance.

All material and images on these pages are copyright Joseph,Ed. This page was developed for the Thinkquest1999 competition.