| A basic two way communication system consists | | | | operation within a radius of several miles |
| of base station or base and one or more | | | | from the base station or repeater system. |
| mobile units or mobiles. The base station | | | | Many radio repeaters are interconnected with |
| with its control or operation point is | | | | the telephone lines so that mobile radio |
| usually centrally located in a city building. | | | | operators, equipped with push button key pads |
| The mobiles communicate with the base by very | | | | in their transceivers, can gain access to the |
| high frequency or ultra high frequency | | | | lines. |
| transmitter and receiver sets most often | | | | |
| configured as transceivers. | | | | An autopatch is a device for connecting radio |
| | | | transceivers to the telephone line by remote |
| A transceiver is a combination of transmitter | | | | control. Autopatch is generally accomplished |
| and receiver having a common frequency | | | | through repeaters. |
| control and usually enclosed in a single | | | | |
| package. Transceivers are used extensively in | | | | A portable telephone is a radio transceivers |
| two way radio communication at all | | | | designed for access to an autopatch system. |
| frequencies and in all modes. Another | | | | Portable telephone resembles handsets with |
| operation that is usually performed is duplex | | | | antennas. There are two types of portable |
| operation or simply duplex. It is a form of | | | | telephones. The short ranged variety is |
| radio communication in which the transmitter | | | | called cordless or wireless telephone. It is |
| and receiver of both stations are operated | | | | designed for use within a few hundred feet of |
| simultaneously and continuously. Each station | | | | a base unit. The long range type is similar |
| operator can interrupt the other at any time, | | | | to a walkie talkie and its range is limited |
| even while the other is transmitting. | | | | only by the access range of the autopatch |
| Therefore a normal conversation is possible | | | | repeater and transceivers which is typically |
| similar to that over telephone lines. There | | | | ten to twenty miles. |
| are no blind transmitters and therefore there | | | | |
| is no need to exchange signals such as over. | | | | A cordless telephone uses a radio connection |
| | | | between the receiver and the base rather that |
| Break in operation is a form of radio | | | | the usual cord. Two small antennas one at the |
| communication in which a transmitting | | | | main unit and other at the receiver allow use |
| operator can hear Mobile telephone is a radio | | | | of the receiver from six hundred to eight |
| transceivers designed for access to autopat | | | | hundred feet. |
| system. Mobile telephones since they involve | | | | |
| radio transmission cannot easily be used in | | | | A pager is a receive only device, activated |
| some countries without a license from the | | | | by a two tone signal from the base station |
| government. Mobile and portable telephones | | | | that sets off a series of audible beeps to |
| usually operate in the very high frequency | | | | alert the carrier to report to the base |
| and ultra high frequency radio bands, between | | | | station or call the base station by |
| about thirty megahertz to three gigahertz. | | | | telephone. |
| This frequency range provides reliable | | | | |