PURPOSE: To realize highly efficient coding and to attain effective utilization of a radio frequency by conducting the coding not only in the unit of charcters but also in the unit of phrases and words, when possible, in the calling communication system transmitting a sentence to a radio terminal device.

CONSTITUTION: A subscriber inputs a simple sentence from a keyboard of a terminal device 1. An exchange 3 for calling communication decomposes the received sentence into components in the unit of phrases, words, characters, numerals and symbols, indexes a conversion dictionary stored in a memory 7 and converts the components into numeral codes corresponding to respective phrases and words or the like. Further, the numerical code converted in this way is transmitted from a radio base station 8 together with the number of a radio terminal device 9. The radio terminal device 9 decodes the received numeral code by using a table, forms the original sentence and displays it or outputs in the form of synthesized voice.