Category Communication

Today, the postman delivers your letters to your doorstep, but it was not always like that. In the early part of the 19th century, envelopes were not used. Instead, a letter was folded and the address placed on the outside of the sheet. The customer had to take a letter to the post office to mail it, and the addressee had to pick up the letter at the post office. In big cities in the USA, mail would be delivered home if you paid the carrier. In 1863, free city delivery was instituted in 49 of the largest cities in the USA. By 1890, 454 post offices were delivering mail to residents of United States cities. It was not until the turn of the century, however, that free delivery came to farmers and other rural residents

You might have seen your parents give a letter to someone who is going abroad so that they can pass it on to your relative who lives there. Well, in earlier times, when there were no postal services, this was how letters and messages were sent. This method of using travelers to deliver messages to other places developed into a system known as post riders.So we can say post riders were a horse and rider postal delivery system that existed at various times and various places throughout history. Post riders collected and delivered mail over the course of their route, meeting with other riders at scheduled times and scheduled places. Letters and parcels would be exchanged and forwarded to the next place by the riders. In this way, messages could pass a considerable distance

Airmail is mail that is transported by aircraft. It arrives more quickly than mail that comes by road or ship, which is called surface mail. Airmail also costs more to send. If you want to send an urgent letter overseas, you have to send it by airmail. If you send it by ship, it could take weeks. In the case of airmail, the letter would reach its destination in days.

Today, the postman delivers letters to every home. In the past though, the post was a privilege enjoyed only by kings and emperors. They used runners to carry messages to other rulers and to their commanders during times of war. A king would have a message inscribed on a clay tile and send a runner to take it to anotherHowever, the ancient Egyptians though did have a kind of postal system and so did the ancient Chinese. The early postal systems depended upon post houses that served the carriers of messages or mounted messengers. The Romans created the most highly developed and dependable system in the ancient world. This system could deliver messages 270 kilometers in 24 hours

You can say that wireless communication is communication that requires no wires! To put it more accurately, it is communication that takes place through the air, using radio waves or infrared light. There is no need for cables or telephone lines for wireless communication. Wireless communication systems use devices called transmitters to generate radio waves. A microphone or other device converts sound or other data into electrical impulses. The transmitters change the impulses into radio signals that can be sent across great distances. Radio receivers pick up these signals, and turn them back into the original sound or messages.Wireless communication has also become a part of our daily life. It is used in our radios, televisions, mobile phones, remote controls and security systems. Wireless communications are a rapidly growing segment of the communications industry, and have mind boggling applications for the future.

You must have heard of planes and ships being located by radar, but what exactly is radar? It is a scientific method to detect and locate moving or fixed objects by using radio waves. In fact, the full form of the word ‘radar’ is ‘radio detection and ranging’. Radar can detect the distance, height, direction and speed of objects that are much too far for us to see. It does this by sending radio waves towards an object, and receiving the waves that are reflected from an object. The time it takes for the reflected waves to return from an object tells us how far away it is. The direction from which the reflected waves return tells us where the object is located.Radar can find anything from tiny insects to huge mountains. It is extremely useful as it works at night too and is not affected by the weather. In fact, it is used by weather departments to make forecasts. Radar is used to control the movement of aircraft and ships, and even to catch your father if he is over speeding!