The two-way radio is aptly named, as it can both transmit and receive signals. Unlike an ordinary one, it also allows you to speak into a station, while transmitting messages from that station to several other users within that geographical area.
There is always a central control room from where the transmissions are relayed to all the devices present in that area, and users on the field can speak into their own sets to relay messages back to the station.
This is the common two-way radio that we see on television, such as in the series Cops. They are the ones that are used by security services, including the police. However, the option of one user being able to listen to what the other user is saying, may not always be used, for confidentiality purposes.
Generic messages from the station can be heard, and every user can speak to the station, but in most cases, they cannot speak with each other over the device.
In typical slang, it is also called a walkie-talkie. The ham radio is quite different from this device. Ham radios do not have a station; they allow people to speak with each other.
Contrary to popular belief, they are not an American invention. The first walkie-talkies (the form that is being used nowadays) were developed by Frederick William Downie, a Senior Constable with the Victoria Police of Australia.
This department was also the first to use these radios in their cars, which vastly improved their methods of communicating, while on the move. Just a little tidbit - the first ones used in the world, were in the Lancia Police Cars of the Victoria Police. They would occupy half of the car, leaving only the driver's seat empty. Now, imagine that!
Today, of course, the technology of wireless communication has advanced tremendously. In the general sense, the two-way radios work on two frequencies, one for sending and one for receiving.
In order to activate the sending, you have to push the 'talk button' and in order to activate the receiving, you have to press the 'transmit button'. Most devices will have one of these functions in default, and you will need to press a button for activating the other function.
The following are some of the popular kinds that are used today:-
- Single Channel and Multichannel Radios - Most conventional two-way radios operate on one channel at a time, which is selected initially by the people who are using it. Some are multichannel, and because of that, they can be put to multiple uses.
- Trunked Radios - In these, the user does not select the channel, but the device itself picks up the right frequency. On these, several communications can occur on one physical channel.
Apart from these, there are several walkie-talkies that are used for recreational purposes, especially by children. Some newer and sophisticated versions of the walkie-talkies have entered the market, like the 40 channel CB radios, which are popularly used by adults, who want to conduct two-way conversations.
Theoretically speaking, even the cell phones used today will qualify as two-way radios, because they also allow two-way communication between two people, by using two different frequencies. You can even invite other people to join a communication on the cell phone, through a conferencing option.
All two-way radios have a range of operation. They can be used within this range. Some newer ones are capable of sending and transmitting information over longer distances, but this might be subject to legislation within the area. The use of these devices is strictly controlled by governmental laws in most areas of the world.