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