# 6.1 Explores signals and their properties

At the beginning of this competency, you have to learn about signals and their properties. The communication is referring to exchanging information or messages in between two or more parties. When it comes to the Data communication it describes about how electronic data is transferring in between two or more parties through a transmission medium. In this concept, that electronic data is transferring as a SIGNAL. There are two types of signals. Analog and Digital. Both of types can be illustrated as graphs. See below figures.

This is how an analog signal is looks like. There are several characteristics or properties in a signal.

1. Amplitude
2. Frequency
3. Wave Length
4. Phase

Amplitude is also known as voltage, height or power of a signal. And it usually defined as volts. That is defined as X in above figure. Voltage level can be negative or positive. In analog signals, the amplitude can be raising from zero volts to positive infinity or can be reduce down from zero to negative infinity.

Frequency is the number of waves or cycles that can pass in a given specific time period. In above figure point A to point B is a complete cycle or wave. Frequency is measured by Hertz(Hz). One hert is equal to one cycle. When the cycle rate in increasing, following units are use to represent the frequency.

1000 Hz = 1 KHz (Kilo Hertz)
1000 KHz = 1 MHz (Mega Hertz)
1000 MHz = 1 GHz (Giga Hertz)

Wave length is the distance between two specific points in a signal. That is represented as Y in above figure. Also is is measured by the unit called lambda. Last one is the phase. The phase is to use describe a specific location within a given cycle of a wave. Assume that the same signal is moving its current location with the time. If you selected any point of the signal, you will have other locations that parallel to current point. But the important thing is, other points also should be doing the same thing or same angle with the selected point. The phase is measured by the angle.

Above picture shows how digital signal can be represented. The problem when working with analog signals is that analog wave does not have a limited amplitude and a shape. Therefore, it was a critical problem when dealing with electronics. Digital signal was solved that problem with limiting for only two states. Digital signal also has above properties. Sometimes you can see negative part of a digital signal. But usually it represents two voltage levels only. Zero level and other specified voltage level. You will learn more about this signal properties in later posts those are corresponds to other competencies.

Apart from these properties of the signal, you have to learn other small part in this competency level. Which is propagation speed in a media.

Simply in data communication, the propagation speed means that, the data capacity or electronic bits can be transmitted through a medium in a given time. Data is travelling as electronic bits. Therefore, the propagation speed is measured by Bits Per Second (bps) unit. When bit number is increasing, we can use Kbps, Mpbs and Gbps units as well.

1000 bps = 1 Kbps
1000 Kbps = 1 Mbps
1000 Mbps = 1 Gbps 