The transmission losses in wire and radio communication are compared for various frequencies and distances of transmission. The effect of natural and signal interference at the receiving ends of such systems is described, and conclusions drawn as to the necessary minimum transmission levels to be maintained in wire and radio circuits. The limitations on two-way operation resulting from "singing" of the entire system are considered in each case, and for combination wire and radio circuits as well. The comparative usefulness of repeater stations for wire and radio used is derived. Several means of effective wire and radio telephony are described, notably transmission on one side band only. The transmission requirements in numerical form of a radio telephone system are then given.