Radio Station, Low-Level

a fixed or mobile radio transmitter-receiver used to provide service or industrial (low-level) radiotelephone communications. Low-level radio communications are used (mainly as traffic control communications) in the direct control of operations in individual enterprises or the production subdivisions of enterprises, in the organization of passenger service and traffic control in railroad transportation (seeRAILROAD RADIO COMMUNICATIONS), in aviation, in taxi services, and in river and marine transportation. They are also used in communications with individual prospecting groups in geological expeditions, in the militia, in fire departments, and in ambulance services. In agriculture, low-level communications are used in the control of farm operations, tractor teams, sovkhoz departments, and kolkhoz teams and in transhumance.

In a typical design of a low-level network having separate subdivisions serving a particular territory, such as that of an enterprise or kolkhoz, the radio stations are usually subdivided into a control and several subordinate (subscriber) stations. Communications are not usually provided between the subscriber stations or between the separate network subdivisions. Each subscriber station is assigned an individual number for selective calling. As of the mid-1970’s, low-level radio stations feature subscriber calling that is completely automatic and is accomplished by dialing the subscriber.

The transmitters in such communications have moderate power ratings—up to 50 watts for control stations and up to 10 watts for subscribers’ stations—and use frequency modulation or (rarely) single-side-band modulation. The stations operate in radio-frequency ranges specially allocated for them by radio-communications regulations. Stable communications can be achieved up to several hundred kilometers in the decameter-wavelength range and up to several tens of kilometers in the meter and decimeter ranges. The stations are intended for service under various, often unfavorable, radio-communications conditions and provide communications that are adequate for high-quality duplex or simplex telephony without the need for searching or tuning.