Analog transmission is the traditional method of sending and receiving telecommunications signals. These signals are sent in the form of waves, which duplicate the transmission as it was picked up at the source or input. An analog transmission is sent over a single channel. Radio, television and phone analog transmissions can be translated into digital signals with the use of certain devices that convert the wave into digital or binary format.
Before the introduction of digital receivers and devices, all radio, television and telephone signals were sent through analog transmission. In fact, most digital transmissions simply convert analog waves into binary format in order to achieve increased channel capacity. For example, much of the wireless telecommunications industry employed this concept as it made the switch from analog to digital devices. As demand for service increased, it was necessary to upgrade cell towers and switch subscribers to digital phones in order to accommodate the jump in the level of voice transmissions.
An analog transmission duplicates the sound or picture from the original source. In a voice transmission, an analog signal represents a sound wave. The replica of the sound wave is sent as electricity through a wire and then converted back into a sound wave at the receiving end. In the case of analog cable television transmissions, a replica of the picture is sent through the cable and converted back into its original form.
The main difference between analog transmission and digital is that digital operates under the binary system. Voice or picture signals are converted into numbers before they are transmitted. Under the binary system, a series of zeros and ones are used to represent and send the signals. Analog, on the other hand, simply creates an identical version of the original.
Another difference between analog and digital transmissions is that analog signals are transmitted continuously. In other words, the signals are always present over a specific range. Digital signals can be either "on" or "off" according to their binary code. Analog signals can also vary over a certain amount of time.
There tends to be more noise or interference with an analog transmission. This is because the signal waves tend to amplify sound, which means that any static or other noises that may be picked up during the transmission are also amplified. In contrast, digital transmissions tend to be more precise and accurate once they are received. The rate of errors that occur during transmission also tends to be higher with the use of analog based technology.