A basic two way communication system consists of base station or base and one or more mobile units or mobiles. The base station with its control or operation point is usually centrally located in a city building. The mobiles communicate with the base by very high frequency or ultra high frequency transmitter and receiver sets most often configured as transceivers.

A transceiver is a combination of transmitter and receiver having a common frequency control and usually enclosed in a single package. Transceivers are used extensively in two way radio communication at all frequencies and in all modes. Another operation that is usually performed is duplex operation or simply duplex. It is a form of radio communication in which the transmitter and receiver of both stations are operated simultaneously and continuously. Each station operator can interrupt the other at any time, even while the other is transmitting. Therefore a normal conversation is possible similar to that over telephone lines. There are no blind transmitters and therefore there is no need to exchange signals such as over.

Break in operation is a form of radio communication in which a transmitting operator can hear Mobile telephone is a radio transceivers designed for access to autopat system. Mobile telephones since they involve radio transmission cannot easily be used in some countries without a license from the government. Mobile and portable telephones usually operate in the very high frequency and ultra high frequency radio bands, between about thirty megahertz to three gigahertz. This frequency range provides reliable operation within a radius of several miles from the base station or repeater system. Many radio repeaters are interconnected with the telephone lines so that mobile radio operators, equipped with push button key pads in their transceivers, can gain access to the lines.

An autopatch is a device for connecting radio transceivers to the telephone line by remote control. Autopatch is generally accomplished through repeaters.

A portable telephone is a radio transceivers designed for access to an autopatch system. Portable telephone resembles handsets with antennas. There are two types of portable telephones. The short ranged variety is called cordless or wireless telephone. It is designed for use within a few hundred feet of a base unit. The long range type is similar to a walkie talkie and its range is limited only by the access range of the autopatch repeater and transceivers which is typically ten to twenty miles.

A cordless telephone uses a radio connection between the receiver and the base rather that the usual cord. Two small antennas one at the main unit and other at the receiver allow use of the receiver from six hundred to eight hundred feet.

A pager is a receive only device, activated by a two tone signal from the base station that sets off a series of audible beeps to alert the carrier to report to the base station or call the base station by telephone.